Aquatic Adventures
Aquatic adventures take many forms: A dark, still lake, in which lurks a terrible monster; a great underground cataract, thundering and racing down through measureless caverns; a sunken city dreaming beneath the glassy waves of a tropical sea; a cold and forbidding island in the fogbound waters of the north, where a cabal of necromancers practice their grisly craft.
Adventuring in or around the water revolves around one of four basic themes: the water obstacle, the seafaring adventure, the mythic-island adventure, and the underwater adventure.
The water obstacle is the most common maelstrom environment most adventurers encounter. In the course of exploring a dungeon of some kind, the party encounters a room filled with water. It might be an underground river barring their progress, a subterranean lake of unknown extent, or simply a fiendishly effective trap or barrier designed to limit the heroes' progress. In order to overcome the obstacle, the characters must subject themselves to a difficult and dangerous environment in which their strengths are largely negated, or they must make resourceful use of magic and skills in order to bypass the watery stretch. Monsters better adapted to water than most player characters naturally make great use of water obstacles; heroes fighting aboleths or kuo-toas should not expect to defeat their foes without getting wet sooner or later.
Seafaring adventures are typically what most people envision as an adventure set on or around the sea. The heroes are traveling to a distant, exotic land, or hunting down a vicious gang of pirates, or are pirates themselves - perhaps good-hearted rogues and scoundrels who battle against the tyranny of an evil empire, perhaps murderous plunderers and killers who rob and pillage their way across the seas. Some campaigns are built around seafaring adventures, but usually a seafaring adventure is a single chapter in the heroes' career: a single memorable adventure for characters who soon return to more conventional dungeon adventuring. Seafaring adventures can use a voyage solely as a story mechanism, a way to move the heroes to some exotic foreign locale, or the voyage itself might be the adventure.
The mythic-island adventure is a variation on the seafaring adventure. For thousands of years, islands have been regarded as places of mystery, idiosyncratic worlds where all kinds of strange things might be true - an island occupied solely by hill giants, where everything else is giant sized; an island of the undead, where vampire nobles rule over courts of ghouls, ghasts, and mohrgs; an island of deadly beauty, in which seemingly innocuous creatures are merciless foes. A mythic island is a microcosm in which any or all normal expectations might be reversed. It might be as simple as a jungle island where the heroes confront an array of monsters they don't normally encounter, or it could be as complex as an island city-state where magic use is horribly dangerous and wizards therefore arrested on sight. Heroes exploring the campaign's mythic islands could be in for almost anything and must adapt their expectations and tactics to suit the particular conditions of each island they encounter.
Finally, underwater adventures are truly unusual. The sea itself is an exotic locale, a realm of marvels and terrors that landbound adventurers can scarcely imagine. The heroes might be hunting a deadly sea monster terrorizing the towns of the coast, exploring the magnificent ruins of a sunken city, or descending into the black and lightless depths of a dark, still lake in search of a lost artifact. Unlike a water obstacle in a dungeon, an underwater adventure requires a long-lasting and durable adaptation to water, since the characters might spend days or even weeks submerged. Powerful magic of some kind (a water breathing spell, a polymorph any object spell to change a human into a merfolk, or a magic item such as a cloak of the manta ray) will certainly be required for success unless the characters are already members of aquatic races.
Seas And Oceans
The first thing that leaps to mind in regards to aquatic adventuring is, naturally, adventures in and around seas and oceans. The sea is often regarded as the realm of chaos, the darkness and disorder that existed before anything else was created. It is powerful, majestic, and utterly capricious. Heroes who venture into this realm of chaos and terror represent the boldest (or most foolhardy) of adventurers, daring storm, shipwreck, starvation, sea monsters, and the wrath of the gods themselves. Storytellers and poets of dozens of cultures use the sea to frame stories of adventure, exploration, and sheer fancy-since who can say for certain what might lie over, under, or beyond the sea?
Seas and oceans aren't just places to go have adventures. They are also the great roads of the world, a vast commons on which the trade, communications, and warfare of a hundred coastal lands depend. Even in the fantastic world of the DUNGEONS & DRAGONs game, a sturdy sailing ship offers the fastest and safest way for most people to travel or send any large volume of goods from one place to another. Most merchant ships stick to short, safe, well-charted routes, hugging familiar coastlines as they ply the waters between their ports of call. Only the boldest and most intrepid of merchants dare crossings that keep them out of sight of land for more than a day or two, or routes that carry them along dangerous and unfamiliar coasts.
Rivers
While the power and majesty of the sea is an obvious source of inspiration, waters of all kinds are imbued with mythic power. Rivers bring life, trade, and prosperity to many lands or offer mysterious routes deep into unexplored lands for those who dare to follow them.
Rivers are natural obstacles to people traveling by land. Shallow or slow-moving rivers can be forded, swum, or rafted over, but any river crossing entails hard work or risk. A party of travelers can lose a horse or two while swimming or fording a swift-running river. Valuable goods might be soaked or lost. Finally, wading or swimming a river exposes a party to the danger of unseen monsters in the water who might strike when the travelers are at their most vulnerable. Because good-sized rivers are such formidable obstacles, crossing points such as fords, ferries, or bridges are vitally important chokepoints for trade and travel - and all too often attract monsters, thieves, or brigands.
While rivers are challenging obstacles to overland travel, they are a quick way to travel if you have a sturdy raft, canoe, or boat. The choice of directions is somewhat limited, but travel by boat between two towns on the same river is usually far faster and safer than walking or riding. As with seagoing ships, a well-made raft, barge, or keelboat can move much heavier cargoes than any train of wagons or carts moving by road. Broad, slow-moving rivers in civilized lands form vital highways that carry enormous amounts of commerce. Rivers in unsettled or unexplored lands will probably not carry trade, but they do offer parties traveling by boat an easy and comfortable journey compared to exploring on foot.
Of course, not all rivers are suitable for navigation. Rapids, shallows, or waterfalls block travel or, worse yet, can pose sudden dangers to parties.
Lakes
Much like rivers, large lakes are challenging obstacles to parties traveling by land, and broad, easy roads to parties traveling by boat. lakes can rarely be forded or swum - travelers must detour around them, or obtain a boat to cross.
Lakes, like seas, often hold an element of mystery and myth. Each lake is its own world, a tiny domain of the unknown in the middle of a familiar land. Very large lakes are seas in their own right, great waters that can be stirred to frightful storms or haunted by terrible monsters of the deeps. Lakes in beautiful natural settings such as high mountains or mist-bound forests are places of great natural power, and can be home to powerful and capricious fey. Even relatively small lakes are often home to untamed spirits or sinister monsters, or serve as gateways into hidden worlds.
Coasts And Islands
Lands touched by the sea or surrounded by great waters are often places of rare peril. Removed from the mundane world of humankind, the intervening waters, exotic coasts, or lonely islands often hold hordes of monsters, dire enchantments, or insidious dangers. The songs of harpies or sirens, the malevolent magic of evil sorcerers, dragons in their lairs, chained demons, or bloodthirsty gods of stone and iron all await to destroy those who intrude upon their domains.
Particularly remote, desolate, or hard-to-reach islands often serve as worthy destinations for the boldest of adventurers. In general, the farther you sail and the more dangers you pass through, the greater and stranger the wonders you will find. In the most remote reaches of the sea lie islands where the very nature of the world frays and changes, places where the thin, cold winds of the seas beyond the world carry many strange and terrible things to rest.
Even familiar coasts or settled islands hold a hint of the extraordinary about them, for any coast is a place where the two worlds - the world above the waves and the world below - meet and interact. Ancient port-towns are home to far-traveled mariners, who whisper of distant wonders and unimaginable horrors waiting across the face of the deep. Desolate and empty coasts hold the hidden lairs of bloodthirsty pirates and the lonely towers of sinister wizards. The coastal waters are home to many sea folk, such as aquatic elves, locathah, and sahuagin, as well as larger monsters such as scrags, merrow, and giants.
Caverns And Dungeons
Many adventurers encounter maelstrom environments and challenges in the most unlikely of places - the deep tunnels, caverns, and dungeons of the world. Subterranean waters fall into one of five general categories: pools, wells, and canals; underground rivers; underground lakes and seas; sea caves; and marine caverns.
Subterranean waters are usually quite cold, unless warmed by hot springs or other geothermal activity. Characters who enter cold water are subject to hypothermia. They are also pitch black; unless a character has darkvision or a waterproof light source, it can prove almost impossible to navigate the depths of a subterranean lake or pool.
Pools, Wells, And Canals
Dungeon and fortress builders often include extensive water features in their construction. In the first place, any complex intended for extended habitation must have a good source of clean water. Secondly, water features form excellent defenses, forcing invaders into difficult and time-consuming detours. Water can be very useful for transportation and performing work, even underground. Finally, many cultures and races revere water and admire its use in architecture, and therefore use it for decorative or ceremonial purposes in places such as temples, plazas, or palaces.
Sophisticated use of water features signifies a good deal of skill in stonework and subterranean construction. Dwarven citadels often include extensive water features, some of which can be natural underground waterways the dwarves incorporate into their structure, as well as canals, waterwheels, or fiendish flooding traps to defend the citadel. Kuo-toa strongholds include even more extensive water features; kuo-toa temples are often surrounded by large pools, with various parts of the complex reachable only through flooded tunnels.
Underground Rivers
Many of the greatest and most extensive cave systems were carved over millennia by flowing water. Underground rivers are generally more precipitous than surface rivers, and therefore much less navigable - they are obstacles, pure and simple, and only the boldest or most desperate of adventurers would attempt to ride one into unknown depths when catastrophic rapids or dizzying lightless cataracts might wait around every bend.
Underground rivers have portions that completely fill the passage they follow, leaving no air space above, and portions that fill the bottom part of larger tunnels, leaving room for breathing (and possibly boating). Water runs downhill, of course, so underground rivers rarely emerge into daylight unless they begin in an area of high elevation (inside a hill or mountain) and emerge in an area of significantly lower elevation. Most underground rivers simply descend lower and lower until they vanish into the gloomy abysses of the deep Underdark, tumbling in miles-high cascades into great Underdark seas.
Underground Lakes And Seas
Somewhat less dangerous than underground rivers, subterranean lakes and seas are the largest water features to be found underground. As on the surface world, a lake or sea serves as a broad and easily traversed highway for travel, provided you have a boat - but boatmaking materials tend to be in short supply in the Underdark, so relatively few people can avail themselves of this mode of travel.
Underground lakes often have completely submerged sections, places where the cavern roof descends to meet the surface of the water, leaving no air overhead. Long, water-filled passages pose a considerable challenge to air-breathing characters. Underground lakes represent valuable territory in the Underdark; supplies of fresh water often attract monsters, and few large lakes aren't home to some unpleasant denizen or another that sits comfortably atop the local food chain. Underground seas are simply lakes of enormous extent, sometimes hundreds of miles across. Great columns miles thick support the incalculable weight of the sea's roof, forming towering islands whose mountaintops meet the cavern ceiling. As with smaller underground lakes, extensive portions of an underground sea can fill caverns right up to the roof, offering air breathers no passage without resorting to magic.
Underground lakes and seas are the demesnes of the terrible aboleths, whose sunken cities lie deep in the black and lightless waters.
Sea Caves
Mountainous or rocky coasts commonly feature numerous sea caves, created through the ceaseless battering of waves against rock. Sea caves are naturally found close to sea level; deep underwater, there's no wave action to speak of, and the sea can't reach very high above the normal high-tide line. Sea caves often have partially flooded entrances (or entrances flooded at high tide), permitting swimmers or small boats to enter under the right conditions.
Sea caves usually offer a mix of flooded and dry chambers, although surging wave action can make flooded portions of the cave dangerous to enter - weak swimmers can be swept away or battered against the cave's rocky walls.
Marine Caverns
Finally, marine caverns are great cavern systems in the sea bed. Some are vast, flooded caverns in the deep seafloor, huge abysses that serve as lairs to the largest and most powerful marine monsters. Others are the mouths of underground rivers that can stretch for miles only a few dozen feet below the surface of shallow sea bottoms and low-lying land. Another type of marine cave is the blue hole, often found in warm, relatively shallow waters. A blue hole is a collapsed sinkhole that was formed on dry land but then inundated by rising sea levels. Blue holes often have extensive limestone cavern systems extending from the sides of the central hole.
Usually these vast caverns are completely flooded, creating lightless gulfs where even the most fearsome sea monsters rarely go. Occasionally, however, some marine caverns have water-filled passages that lead to air-filled spaces below the seabed. These fantastic caverns can be hundreds or thousands of feet below the ocean surface and lead into vast "lost world" caverns hidden beneath the sea.
Fresh Water Versus Salt Water
The DUNGEONS & DRAGONS game does not distinguish between creatures that live in freshwater, creatures that live in saltwater, or creatures that can survive in either. Most monsters are completely insensitive to the difference - you can find aboleths in the bottom of Underdark rivers and seas or in the deep ocean trenches. The encounter tables (Stormwrack Appendix) reflect an implicit division of animals and monsters into creatures found in fresh water (nixies) and creatures found in salt water (aquatic elves or sahuagin), but otherwise an aquatic creature is an aquatic creature.
At the DM's discretion, creatures that belong in the other kind of water must make a Constitution check once per hour (DC 10, + 1 per previous check) or take 1d6 points of nonlethal damage. Creatures who take damage from a saltwater or freshwater environment become fatigued and remain so as long as they remain in an environment they aren't suited for.
Planar Seas
Beyond the Material Plane lie seas of literally infinite extent, enticing bold-hearted mariners with access to powerful magic to explore oceans few mortal eyes ever behold. Many of the dangers described in Water Hazards below are significantly larger, stronger, more prevalent, and more malevolent on other planes of existence.
Elemental Plane Of Water
The Elemental Plane of Water is the ultimate origin of the maelstrom and all its wonders and perils. The great oceans and mighty rivers of the world are manifestations of elemental power, and direct portals linking the Material Plane and the Elemental Plane of Water can be found in the ocean deeps and the springs from which the largest rivers flow. Creatures native to the Elemental Plane of Water often visit the seas of other worlds, and so monsters such as tojanidas, marids, and elementals are common in such areas.
A visit to the Elemental Plane of Water is a daunting challenge for air-breathing characters, but water-breathers can manage it easily. The great majority of the Elemental Plane consists of nothing but water, so vessels designed to travel on the surface have no business entering this plane. However, there are rare places in the Elemental Plane where great pockets or islands of Elemental Air intrudes, forming titanic bubbles that can be dozens or even hundreds of miles across. A bold captain who knew exactly which portal to take could bring a ship to the interior surface of such a bubble and sail on the inside of a spherical air pocket within the Plane of Water.
Characters exploring the Elemental Plane of Water in the conventional fashion (swimming and breathing water) find a world that looks very much like the depths of any Material Plane ocean. There is no bottom and no surface, but suspended within this universe of water lie all sorts of debris and jetsam - great drifting rocks and boulders from the Elemental Plane of Earth, huge forests of kelp and seaweed, and tremendous currents and eddies that can wash a traveler miles out of his way.
Naturally, elementals with the water subtype are quite common on the Elemental Plane of Water. A great variety of sea life of all sorts, including monsters such as krakens and morkoth, also lurk within the endless deeps. The Plane of Water is home to the race of tritons, and marids (the most powerful of genie kind) dwell here in great palaces of pearl and coral.
Abysm
The realm of Demogorgon, the 88th layer of the Abyss is a plane of briny water broken by rocky prominences. Demogorgon's palace is a great serpentine double tower, each crowned by skull-like minarets. Below this mighty fortress extend measureless chill and darkened caverns. Fiendish aboleths, krakens, and ixitxachitl roam the foul seas of Abysm, warring incessantly with each other.
Porphatys
The fifth layer of Carceri is a infinite string of worldlets covered in cold, shallow oceans over which acidic black snow perpetually falls. Low islands scarcely bigger than sandbars rise above the waves. A great white caravel known as the Ship of One Hundred roams the seas without benefit of crew or master, although stranded travelers sometimes board the sinister vessel and remain for a time, hoping that the ship's wanderings might bring them to a portal from which they can escape Porphatys.
Stygia
The fifth layer of the Nine Hells is a great, frozen sea covered in crushing ice floes and icebergs. The only open water is the Styx itself, a broad, winding lead of dark water half choked with ice. Stygia offers ships few places to sail other than the river itself, but its ocean extends for an infinite distance beneath the mighty icecap.
Lunia
The first of the Seven Heavens, Lunia is girded by the dark, starry Silver Sea. Its shores are dotted with the white citadels and redoubts of Celestia's residents, and its deeps are home to many good-aligned aquatic creatures, including celestial whales and aquatic elves.
Thalasia
The fourth layer of Elysium is Thalasia, the source of the great River Oceanus that winds among the upper planes. Thalasia's great sea is dotted with fair green islands, known as the Blessed Isles, Avalon, or the Isles of the Holy Dead. Many great heroes rest here, waiting for the day they are needed again. The sun deity Pelor inhabits a mighty citadel in Thalasia.
Aquallor
Second of Arborea's layers, this mighty ocean is without islands or shores. It marks the end of the River Oceanus. Tremendous storms sweep its surface, and in its darkest depths lie vast maelstroms that lead back to Oceanus's headwaters in Thalasia. Aquallor is home to many aquatic elves and sea creatures of all sorts, including the elf deity Deep Sashelas, who rules the plane from his palace of coral, gold, and marble.
Water Hazards
Water holds a number of dangers for the unwary or luckless adventurer - terrible aquatic monsters, the threat of drowning in dungeon pools or being battered to death in heavy surf, or simply the opportunity to starve or die of thirst on a lost or becalmed ship.
Currents And Streams
Rising or ebbing tides, the draw of heavy surf, the steady flow of a river, or the headlong rush of a fast-moving stream all create powerful currents. Even a relatively slow-moving current can be extremely difficult for a human to swim against. See Flowing Water.
A current has two important traits: direction and strength. If you are in a current (whether swimming or boating), the current moves you in the direction of its flow by a certain number of feet per round at the end of each of your turns. The distance varies with the strength of the current:
| Current Strength | Swimming Speed | Boating Speed | Swim DC |
| Light | 5 ft./round | 1/2 knot | 10 |
| Vigorous | 10-30 ft/round | 1-3 knots | 15 |
| Dangerous | 40-60 ft./ round | 4-6 knots | 20 |
| Irresistible | 70-90 ft/round | 7-9 knots | 25 |
Light currents are found in light surf or slow-moving rivers.
Vigorous currents are found in the draft of heavy surf, in full-rushing rivers, or in areas of very strong tidal flows.
Dangerous currents are found in the draft of very heavy surf, in moderate river rapids, or extreme tidal flows. If you are swept into a solid object (such as a boulder) or a hazardous area by a dangerous current, you might take damage; you take 1d4 - 1 slam attacks per round, each at +2 melee, dealing 1d4 bludgeoning damage for each hit.
Irresistible currents are found in the most violent of rapids, and sometimes in rare undersea bores or jets. If you are swept into a solid object or hazardous area by an irresistible current, you might take damage; you take 1d4 slam attacks per round, each at +8 melee, dealing 2d4 bludgeoning damage for each hit.
Natural swimmers are not immune to powerful currents, but creatures whose swim speeds exceed the speed of a current can at least make headway against it.
Depth
Very deep water deals water pressure damage of 1d6 points per minute for every 100 feet the character is below the surface. A Fortitude save (DC 15, +1 for each previous check) means that you take no damage in that minute.
Any creature with the aquatic type ignores pressure for the first 500 feet of depth, and only takes 1d6 points of damage per 200 feet below that when determining vulnerability to pressure damage. For example, an aquatic elf at a depth of 900 feet is subject to 2d6 points of pressure damage per minute, as opposed to the 9d6 points of pressure damage a surface dweller faces.
Some deep-dwelling creatures are completely immune to pressure damage. Aberrations, elementals, and outsiders with the aquatic subtype are generally immune to pressure damage, as are certain other creatures adapted to the environment (such as giant squids or whales).
Drowning
Obviously, drowning is one of the most immediate and lethal threats posed by a maelstrom environment. You must make Swim checks to remain afloat in water. If you fail your Swim check by 5 or more, you begin to sink, as described in the Swim skill. You can hold your breath for a number of rounds equal to your Constitution score, but only if you do nothing other than take move actions or free actions; each standard action you take reduces the duration for which you can hold your breath by 1 round. After that duration, you must make a Constitution check (DC 10, + 1 per previous check) to continue holding your breath. If you fail the Constitution check, you begin to drown.
Stunned or dazed creatures in the water automatically fail Swim checks, and go under. They do not get an opportunity to draw a breath before sinking and must begin making Constitution checks to hold their breath on the next round after they go under.
Comatose, dying, paralyzed, sleeping, or unconscious characters fail their Swim checks and go under. On the round after they go under, they fail their Constitution checks and begin to drown.
Hypothermia
Cold water can kill quite quickly through hypothermia (the loss of body heat), but surprisingly even water as warm as 70° F or 80° F can kill, given a few hours.
Very cold water is water encountered while the air temperature is cold (40° F) or colder, water in any cold aquatic terrain, and water in deep subterranean lakes and rivers. Very cold water deals 1d6 points of nonlethal damage per minute of exposure. You can negate this damage with a successful Constitution check (DC 15, +1 per previous check).
Cold water is found in moderate air temperatures (40° to 60° F), in temperate aquatic terrain (except in summer), and in subterranean lakes and rivers that are relatively close to the surface in warm lands. Cold water deals 1d6 points of nonlethal damage per 10 minutes of exposure. You can negate this damage with a successful Constitution check (DC 12, +1 per previous check).
Warm water is found when air temperatures are warm or hot (60° F or warmer) or in warm aquatic terrain. Warm water deals 1d6 points of nonlethal damage per hour of exposure. You can negate this damage with a successful Constitution check (DC 9, +1 per previous check).
Creatures native to cold or temperate aquatic environments are immune to hypothermia brought about by exposure to warm, cold, or very cold water. Creatures native to warm aquatic environments are immune to hypothermia from warm or cold waters, and treat very cold water as cold water.
Light
Water is not perfectly transparent; as you descend, less of the sun's light penetrates the water. Sunlight serves as a source of illumination during daylight hours, but sunlight's ability to provide illumination quickly diminishes as you go deeper into the water.
Sunlight as a light source provides the following amount of illumination in the water. Refer to Vision and Light.
| Sunlight As A Light Source | ||
|---|---|---|
| Depth | Bright | Shadowy |
| 30 ft. or less | 100 ft. | 200 ft. |
| 31-60 ft. | 60 ft. | 120 ft. |
| 61-120 ft. | 30 ft. | 60 ft. |
| 121-l80 ft. | 20 ft. | 40 ft. |
| 181-300ft. | 10 ft. | 20 ft. |
| 301 ft. or more | - | - |
Creatures with low-light vision can see objects twice as far away as the given distance, just as they do by torchlight or lantern light. Similarly, creatures with darkvision can see out to the extent of their darkvision.
Murky Water: Water containing a lot of sediment, debris, or organic matter is often quite murky. Most rivers and lakes are murky, while some are very murky.
Murky water reduces the radius of illumination provided by a light source (the sun or a carried light source, such as an object with a light spell cast on it) by 50%, since light scatters and reflects from matter hanging in the water. For example, a sunrod normally provides bright illumination to a range of 30 feet and shadowy illumination to 60 feet, but in murky water these are reduced to 15 feet and 30 feet, respectively.
Very murky or muddy water obscures all sight, including darkvision, beyond 5 feet. Creatures 5 feet away have concealment (20% miss chance).
Sinking And Shipwreck
It's unfortunate but true: Vessels that adventurers embark on seem to meet bad ends with distressing predictability. They are caught up in the storm of a sea god's wrath, they are wrecked on uncharted reefs, they are burned by dragons and crushed by krakens, and all aboard must take to the boats or swim for their lives.
Without consideration for the numerous ways that monsters or magic might destroy a vessel, most ships sink in one of four ways: grounding, battering, foundering, or capsizing. In calm waters, grounding is an obstacle that can usually be overcome with a few hours or days of hard work. Ships that run aground in relatively calm seas aren't completely sunk; it's possible to float a ship free with a lot of work, although a ship with a badly damaged bottom (from running up onto coral or rocks, for example) can indeed sink once it's been pulled free. Ships that ground in mud or sand are in much better condition.
Ships sinking through battering are dangerous places to be - yardarms come crashing down, fittings burst, masts wrench free of their seats, heavy objects come loose and roll or fly about. Every round, a character aboard such a vessel has a 20% chance of being subjected to a slam attack attack bonus +6, damage 1d10) and a 20% chance of being hurled into the water, ready or not.
When the crew loses control of a ship, typically because the helm has broken or the masts fallen, it either becomes a derelict or, if less seaworthy, begins to founder. A foundering ship is at the mercy of the waves and often turns so that green water breaks across its sides. Unless the ship can quickly be turned either into or away from the wind, it will fill with water (when the hatchways give in) and either capsize or sink.
A top-heavy ship (for example, a sailing ship whose sails have become waterlogged) or one that receives a sudden blow from below can capsize. A capsizing ship turns upside down and is completely disabled. While air trapped in the inverted ship can keep it afloat for days or even weeks, it is almost impossible to restore the ship to its proper orientation. Any surviving crew are typically forced to huddle on the exposed hull, without supplies, and hope for rescue. Capsizing is a favorite attack strategy for some aquatic creatures, such as plesiosaurs and dragon turtles.
A ship reduced to a sinking state cannot move (although a powerful wind or current can continue to push the hulk for a time). It takes d% minutes for a sinking ship to finally slip under the waves. Reduce this number by 50% if the vessel is caught in inclement weather, or by 75% if the ship is caught in a storm.
After a ship goes under the surface, it "falls" at a rate of 200 feet per round until it reaches the bottom. Anyone who rides a ship all the way down takes 4d6 points of falling damage when it strikes the bottom.
Special Perils Of The Seas
More than a few adventurers have drowned in dungeon wells or perished in terrible shipwrecks, but the maelstrom holds many other perils for the unprepared or unlucky who venture within its grasp. Strange curses and blights wait in the dark, deathlike waters of lightless caverns and in the foulest reaches of the sea.
Disease
Dangerous diseases found in or around the sea often plague maelstrom environments. See Special Abilities for an explanation of diseases and their workings.
| Disease | Infection | DC | Incubation | Damage |
| Coral scratch | Injury | 12 | 1d4 hours | 1d3 Dex |
| Sea rot | Contact | 20 | 1 day | 1d6 Con + 1d6 Str |
| Sea sores | Ingested | 14 | 1d4 days | 1d4 Str + 1d2 Cha |
| Suntouch | Exposure | 18 | 1 day | 1d6 Wis + 1d2 Con |
Disease Descriptions
The following diseases are often encountered in seafaring environments.
Coral Scratch: Characters who take damage from contact with coral must make Fortitude saves or contract coral scratch. If a character contracts coral scratch, the hit point damage dealt by the exposure to coral does not heal naturally until the character recovers or is cured of coral scratch.
Sea Rot: Usually found in the worst sort of sargasso, sea rot is caused by contact with infected creatures. When a character takes damage from sea rot, he or she must succeed on another save, or 1 point of the ability damage becomes permanent ability drain instead.
Sea Sores: Contracted from eating or drinking food or water of poor quality, such as that found in the stores of poorly provisioned ships.
Suntouch: Caused by heat damage in dead calm. Characters reduced to 0 Wisdom by suntouch are rendered insane instead of comatose, acquiring an overpowering compulsion to immerse themselves in the sea and/or drink seawater.
Poison
Many aquatic creatures are horribly venomous and produce deadly natural poisons. Some of these are commonly harvested by aquatic races and used against their foes. See the accompanying table.
Inhaled poisons generally do not work underwater. However, one inhaled poison (yellow urchin extract) is a thick, milky fluid that is manufactured for use underwater. A single dose creates a faint, milky cloud 10 feet by 10 feet, that hovers in the water for 10 minutes before dispersing (or only 1 minute in a strong current). A creature with the aquatic type (or a creature using water breathing or a similar effect) who enters the poisoned water breathes in this poison, but a creature holding its breath does not.
| Marine Poisons | |||||
|---|---|---|---|---|---|
| Poison | Type | Initial Damage | Secondary Damage | Price | Trap CR Modifier |
| Fire coral extract | Contact DC 13 | Nauseated | 1d4 Dex | 150 gp | +2 |
| Stonefish venom | Injury DC 14 | 1d8 Dex | 1d4 Con | 180 gp | +2 |
| Cone snail venom | Injury DC 12 | 1d4 Con | 1d6 Con + paralysis | 120 gp | +2 |
| Yellow urchin extract | Inhaled* DC 15 | 1d4 Dex + 1d4 Wis | 1d6 Dex + 1d8 Wis | 800 gp | +3 |
| Sea snake venom | Injury DC 16 | 1d6 Con | 1d6 Con | 1,100 gp | +4 |
| Blue anemone oil | Contact | 1d4 Str + 1d4 Dex | Blindness | 400 gp | +4 |
| Sekolah's judgment | Ingested DC 18 | 1d6 Con + nauseated 2d6 rounds* | 3d6 Con | 3,000 gp | +5 |
| * A character who makes the save is nauseated for 1d6 rounds. | |||||
Supernatural Dangers
Powerful and sometimes malevolent magic lurks in the deeps of underground waters and the wide expanse of the ocean. Stormfire plays about a ship's masts in the midst of the most terrible hurricanes, yawning maelstroms swallow ships in otherwise calm waters, and fearsome calms trap seafarers in empty watery wastes until food, water, and hope itself run out.
Avoiding Supernatural Dangers: In general, characters approaching an area plagued by one of these supernatural dangers, or in an area about to be struck by one, are entitled to a DC 20 Survival check to detect the approaching danger 1 minute before it strikes (or immediately before entering the affected area, in the case of a hazard they're moving into).
Airy Water
Considered a boon by any air-breather who encounters it, airy water is a stretch of water that is breathable by both air-breathers and water-breathers. It is filled with streaming effervescent bubbles, and normal marine animals usually avoid it. Airy water is sometimes found in the palaces of good-aligned aquatic creatures such as merfolk, aquatic elves, or even storm giants. Even after such places are abandoned or destroyed by evil, the airy water can remain, allowing surface-dwellers to explore the submerged ruins of these places. Airy water is sometimes found in dungeon water features, offering a secret passage from one place to another to those who know the water's secret.
Characters in airy water are subject to all the normal movement and combat penalties for being in the water - they just have no risk of drowning.
Airy water is typically found in or around specific rooms or chambers and does not often occur in open water (although stories of shallow coral reefs or kelp beds filled with airy water abound).
Airless Water
The sinister opposite of airy water, airless water is a cold, lifeless dead zone. Within a pocket of airless water, aquatic creatures cannot breathe (nor can air-breathers, for that matter). Water-breathing creatures can "hold their breath" in order to enter or pass through a mass of airless water, just as air-breathers can hold their breath to enter water.
Airless water is sometimes incorporated as defenses in submerged strongholds or as deadly traps in dungeon water features, but they are more likely to occur lying close to the ocean floor and sinking down to fill trenches, depressions, and deep places along the bottom. Pockets of airless water have a dark, slightly viscous look that can be detected by observant characters.
Dead Calm
The terrible dead calm is a horror that terrifies even the boldest of sailors. Some portions of the ocean are cursed by evil sea gods and remain forever still and unmoving. No breeze stirs the waters, no current flows to carry a trapped vessel out of the calm. Those who enter all too often die slow, miserable deaths of starvation and madness, unable to escape from the dead calm's grip.
Dead calms are often found in conjunction with vast sargasso mats. In a dead calm, the weather is always hot and still, without a hint of a breeze. Characters in a dead calm who take damage from heat must succeed on a DC 18 Fortitude save or contract suntouch. Dead calms are also notorious for attracting undead such as ghosts, spectres, lacedons (aquatic ghouls), and worse.
Dead calms often have the same effect as a desecrate spell (and the worst dead calms have the same effect as a desecrate spell containing an evil altar or temple, even if no such structure actually exists in the area).
Regions of dead calm normally extend for 10d10 miles. Oared ships can, with some work, free themselves, but sailing ships often have to resort to exhaustive towing work or powerful magic to escape the doldrums.
Maelstrom
Naturally occurring whirlpools are dangerous enough, but some whirlpools are supernatural maelstroms - places where portals to the Elemental Plane of Water, divine manifestations of sea deities' power, or ancient curses have created monstrously powerful vortexes in the water.
Maelstroms come in one of four sizes: minor (10 to 40 feet in diameter), major (41 to 120 feet in diameter), greater (121 to 500 feet in diameter), and immense (501 feet to 2,000 feet in diameter). Maelstroms usually have a depth equal to their diameter.
Maelstroms are surrounded by strong feeder currents that can snare swimmers or boats far from the vortex itself, carrying them within the vortex's grasp.
| Maelstrom Size | Current Strength by Distance | ||
| Strong | Dangerous | Irresistible | |
| Minor | 1000 ft. | 50 ft. | 20 ft. |
| Major | 500 ft. | 250 ft. | 100 ft. |
| Greater | 1,000 ft. | 500 ft. | 200 ft. |
| Immense | 1 mile | 1/2 mile | 1,000 ft. |
Once a swimmer or ship is sucked into the maelstrom by the currents sweeping toward it (or simply has the misfortune of falling into the vortex directly), the target endures three distinct phases of danger: trapped, battered, and ejected. Minor maelstroms can only trap and batter objects or creatures of Huge size or smaller; major maelstroms can trap and batter objects or creatures of Gargantuan size, and greater or immense maelstroms can trap and batter creatures or objects of any size.
| Maelstrom Size | Object Size | Time Trapped | Escape DC | Battered Damage |
| Minor | Huge | 1d4 rounds | 25 | 3d6 |
| Major | Gargantuan | 1d8 rounds | 30 | 6d6 |
| Greater | Colossal | 2d6 rounds | 40 | 10d6 |
| Immense | Colossal | 2d8 rounds | 50 | 20d6 |
Trapped: The creature or vessel is trapped in the whirlpool, slowly being drawn down. Escaping from the trap region requires a successful Swim or Profession (sailor) check against the maelstrom's DC, based on its size. This moves the creature to a square adjacent to the maelstrom (the current doesn't sweep him or her back in immediately but can do so in subsequent rounds). Failing that, the creature or ship is unable to move of its own accord, and revolves helplessly in the whirlpool. At the end of a trapped character's turn, move him or her 30 feet clockwise around the rim of the whirlpool.
Battered: At the end of trapped time, the creature or vessel sinks into the maw of the maelstrom. This takes 1 round, during which the creature or object takes the indicated damage. For ships or vehicles, every section is damaged. Creatures can take no actions in this round.
Ejected: On the next round, the maelstrom ejects the creature or vessel at its bottom. The creature or vessel is now at the bottom depth of the maelstrom. If the maelstrom has a particular exit - for example, a hole in the bottom of a lake, or a portal to the Elemental Plane of Water - the creature or vessel passes through. Otherwise it comes to rest on the bottom or is adrift in the water a short distance from the bottom of the maelstrom's funnel (1d4x10, 20, 50, or 200 feet, depending on the maelstrom's size). A maelstrom without an exit simply generates currents flowing away from it on the bottom with the same strength as currents flow toward it near the surface. Buoyant creatures or objects return to the surface, but there's no reason they couldn't be caught in the maelstrom's grip again.
Stormfire
In the most terrible storms and hurricanes, ships are sometimes struck by stormfire, a capricious and seemingly malevolent phenomenon that has brought more than one vessel to complete ruin. Stormfire gathers slowly, beginning as a faint green phosphorescence dancing along a vessel's rigging and rails. In many cases it proceeds no further; it is simply a disconcerting omen but not dangerous. But sometimes (about 20% of the time) stormfire continues to gather and grow stronger, until suddenly it seems that the whole ship is wrapped in glowing green fire.
A creature entering a square containing stormfire has a 50% chance of being subjected to a brilliant emerald discharge that deals 2d6 points of electricity and 2d6 points of fire damage (Reflex DC 15 half). Stormfire manifestations usually last for no more than 2d8 rounds before guttering out, beginning in one random square on a ship's deck and spreading to one random adjacent square each round until the manifestation ends.
Marine Wilderness Terrain
Adventurers exploring desolate coasts or undersea caves face a variety of challenging terrain, ranging from spectacular coral reefs to the emptiness of the open ocean.
The percentile tables given in each terrain type describe in general terms how likely it is that a given square has a terrain element in it. Don't roll for each square on your battlefield - instead, use the percentages to guide you in creating appropriate maps for the setting. For example, if you are creating a tactical map for a sandy beach featuring 10% driftwood, 20% dune, and 20% gradual slope, and your area covers 10 squares by 20 squares, you can assume that the entire beach will feature sand. About 20 squares on the map will also have driftwood, 40 squares will comprise dune terrain, and 40 squares will be a gradual slope.
Beach Terrain
Beaches include sandy tropical islets, mighty windswept dunes, cold fogbound pebble shores of northerly waters, or even black volcanic sands. Not all coastlines consist of beaches; in many places, land meets water in a broad tidal marsh or mangrove swamp, or along a high, rocky bluff.
The two types of beach terrain described here are sandy and rocky.
| Sandy | Rocky | |
| Boulder or sea stack | - | 10% |
| Driftwood | 5% | 15% |
| Dune | 10% | - |
| Pool or stream | 10% | 10% |
| Rubble | - | 40% |
| Sand, packed | 10% | - |
| Sand, soft | 40% | - |
| Surf, heavy | 10% | 25% |
| Surf, light | 15% | - |
Boulder or Sea Stack: A typical beach rock stands 1d6x5 feet tall and covers 1d6 squares. Boulders or rocks that stick out of the water are sometimes known as sea stacks (some of which can be very large indeed). Beach rocks are usually rough with easy ledges but can be slippery (Climb DC 15), especially if they lie below the high-tide line.
Driftwood: Large driftwood logs washed up on the beach are common near places where forests overlook heavy seas. Sometimes driftwood gathers in great, sprawling heaps of tangled logs, especially after storms. It costs an extra square of movement to cross driftwood, and driftwood provides cover as a low wall.
Dune: A typical dune is 2d6x10 feet long, 1d2x10 feet tall, and three times as wide as it is tall (some can be much, much larger). A dune consists of soft sand and a steep slope; it costs 2 squares of movement to enter each dune square, or 4 squares of movement if you are climbing up its face. Characters running or charging downhill must succeed on a DC 10 Balance check upon entering the first downhill square; mounted characters make a DC 10 Ride check instead. Characters who fail this check stumble and must end their movement 1d2x5 feet later. Characters who fail by 5 or more fall prone in the square where they end their movement. A dune increases the DC of Tumble checks by 2.
Pool or Stream: Tidal pools, stream mouths, or standing seawater trapped behind a sandbar at low tide can be found on many beaches. A pool or stream has shallow water about 1 foot in depth. It costs 2 squares of movement to enter a pool or stream, and the DC of Tumble checks increases by 2.
Tidal pools are normally 1d4x5 feet wide. Streams or bar-trapped ponds are the same width, but can be hundreds of feet long.
Rubble: Pebble beaches are similar to areas of light rubble. The DC of Balance and Tumble checks increases by 2.
Sand, Packed: Wet sand is hard, and comparatively easy to walk on. There are no movement penalties on packed sand.
Sand, Soft: The ground consists of soft, dry sand. It costs 2 squares of movement to enter a square with soft sand.
Surf, Heavy: Heavy surf consists of violently surging water about 4 feet in depth. It costs 4 squares of movement to enter a square of heavy surf, or characters can swim if they wish. Small or smaller creatures must swim to move through heavy surf. Tumbling is impossible in heavy surf. Any creature that begins its turn in a square of heavy surf must succeed on a DC 12 Strength check or Balance check, or fall prone.
The water in a square of heavy surf provides cover for Medium or large creatures, and improved cover for Small or smaller creatures. Medium or large creatures can crouch as a move action to gain improved cover, but creatures with this improved cover take a -10 penalty on attacks against creatures that aren't underwater.
Surf squares are normally found grouped together in a long line. If an area has both heavy surf and light surf, the light surf goes between the heavy surf and the beach.
A wave of heavy surf often has a riptide behind that can draw creatures out to sea (see Currents and Streams).
Surf, Light: light surf has surging water about 1 foot in depth. It costs 2 squares of movement to enter a square of light surf, and the DC of Tumble checks in such a square increases by 2. Any creature that begins its turn in a square of light surf must succeed on a DC 6 Strength check or Balance check, or fall prone.
Stealth and Detection on a Beach: Open, sandy beaches offer little cover; the maximum distance at which a Spot check to detect the nearby presence of others can succeed is 6d6x20 feet. Rocky beaches often have more cover at hand, reducing this distance to 4d6x20 feet.
Tidal Marsh
Large saltwater marshes commonly form where low-lying land meets the ocean. Tidal marshes are often several miles wide, forming a narrow band along the coasts, often protected by sandy barrier islands.
| Bog, deep | 10% |
| Bog, shallow | 20% |
| Creek | 10% |
| Mud flat | 10% |
| Open water | 20% |
| Reeds | 30% |
Bog: Tidal marsh bogs are more accurately called sloughs, wallows, or ponds, but they are otherwise identical to the bog squares described in Bog terrain.
Creek: A creek has the same effect as a deep bog (see Marsh Terrain, but it is normally 1d8 squares wide and meanders across the battlefield.
Mud Flat: A mud flat consists of bare, more or less solid ground. It costs 2 squares of movement to enter a square of mud flat.
Open Water: large pitches of open water interspersed with wet, grassy land make up much of a tidal marsh. Open water is simply water ranging from 5 to 20 feet in depth; it tends to be shallower near land.
Reeds: Stands of tall reeds can be found in shallow water or on land. A stand of reeds offers concealment to anyone who ventures 5 feet into the reeds, and total concealment to anyone who has 10 feet or more of reeds between them and the viewer. It costs 2 squares of movement to enter a square of reeds, and the DC of Tumble checks in such a square increases by 2.
A stand of reeds is normally 1d8 squares wide.
Stealth and Detection in a Tidal Marsh: Tidal marshes tend to be flat and open; the maximum distance at which a Spot check to detect the nearby presence of others can succeed is 6d6x20 feet. However, you're usually not more than a few squares away from a creek, slough, or stand of reeds to hide in, if you don't mind getting wet and muddy.
Coral Reef
Warm seas are renowned for their beautiful coral reefs. Encounters in coral reefs can be 5 on the surface (characters can walk or wade on those portions of the reef that are awash, or submerged by not more than a few feet of water) or under the water (the characters and their adversaries are swimming).
In general, submerged coral reefs occupy water that is 1d8x10 feet in depth, and the coral itself is 1d4x10 feet in eight (but does not rise above the surface in any event, since this will kill the animals whose shells make up the reef). Deepwater corals, though rare, can be found 200 or more feet down. A distinct reef or coral head is a steep-sided underwater boulder, hillock, or plateau anywhere from a few squares across to miles in extent.
Coral reefs that reach the surface (or close to it) occupy water that is 1d2x10 feet in depth, and the reef masses or oral heads are the same height - although deep channels, potholes, or the edge of the reef offer plenty of opportunities to get into deep water.
| Submerged | Surface | |
| Coral, dead | 20% | 30% |
| Coral, living | 20% | 30% |
| Coral, shallow | 20% | 30% |
| Pass | 10% | 10% |
| Pothole | - | 5% |
| Sandy bottom | 20% | 10% |
| Surf, heavy | - | 5% |
| Surf, light | - | 10% |
Coral, Dead: Near or on the surface, dead coral is generally smoother and easier to walk across than living coral. It costs 2 squares of movement to enter a square of dead coral, and the DC of Balance and Tumble checks increases by 4.
Underwater, dead coral forms the bulk of a reef, creating a hard, calcified mass on which the living coral grows. Coral masses are like walls or steep slopes underwater.
Coral, living: living coral is only found underwater. Swimmers of Small size or larger entering a square with living coral have a 50% chance of injuring themselves. The swimmer must succeed on a DC 10 Balance check or scrape against the coral (treat as a melee attack at a +4 attack bonus, dealing 1d3 damage). Any creature injured by coral must succeed on a DC 14 Fortitude save or contract coral scratch (see Disease, above).
Coral, Shallow: Difficult terrain for both swimmers and walkers, shallow coral rises to within 5 feet of the surface or less.
Characters walking or wading on the top of the reef must spend 4 squares of movement to enter a square of shallow coral, or characters can swim if they wish. Tumbling is impossible in a shallow coral square.
The water in a square of shallow coral provides cover for Medium or large creatures, and improved cover for Small or smaller creatures. Medium or large creatures can crouch as a move action to gain improved cover, but creatures with this improved cover take a -10 penalty on attacks against creatures that aren't underwater.
Swimmers of Small size or larger must spend 2 squares of movement to enter a square of shallow coral, large swimmers can't swim in shallow coral.
Shallow coral is potentially dangerous; there is a 50% chance that any character entering a square of shallow coral injure itself, as described under living Coral above.
Pass: A pass is a channel through a reef. It consists of a sandy area on the seafloor with no buildup of coral. Characters walking atop a surface reef have to swim across passes, while characters swimming underwater find that passes permit them to go through a reef without going around or over it.
Passes are normally 1d4x10 feet wide and meander randomly among the reef masses.
Pothole: A pothole is a hidden crevasse or gap in coral that an unlucky wader might step into. A pothole is typically 5 to 10 feet deep. Entering a pothole square means that your move ends, and you are now swimming. A character walking atop the reef is entitled to a DC 10 Spot check to notice the pothole before stepping into it. Anyone falling into a pothole risks injury from the coral (DC 10 Balance check or take an attack as described under Living Coral, above).
Sandy Bottom: A sandy bottom poses no hazard to movement, and large patches or strips of sand serve as safe avenues for walking across an exposed reef. On a surface reef, sandy bottom is normally covered by a foot or two of water, so it takes 2 squares of movement to enter a square of sandy bottom, and the DC of Balance and Tumble checks increases by 2.
Surf, Heavy: Heavy surf consists of violently surging water about 4 feet in depth. It costs 4 squares of movement to enter a square of heavy surf, or characters can swim if they wish. Small or smaller creatures must swim to move through heavy surf. Tumbling is impossible in heavy surf. Any creature that begins its turn in a square of heavy surf must succeed on a DC 12 Strength check or Balance check, or fall prone.
The water in a square of heavy surf provides cover for Medium or large creatures, and improved cover for Small or smaller creatures. Medium or large creatures can crouch as a move action to gain improved cover, but creatures with this improved cover take a -10 penalty on attacks against creatures that aren't underwater.
Surf, light: The edges of a surface reef are marked by surf. light surf has surging water about 1 foot in depth. It costs 2 squares of movement to enter a square of light surf, and the DC of Tumble checks in such a square increases by 2. Any creature that begins its turn in a square of light surf must succeed on a DC 6 Strength check or Balance check, or fall prone.
Stealth and Detection in a Coral Reef: Characters walking on top of a reef are out in the open; the maximum distance at which a Spot check to detect the nearby presence of others can succeed is 6d6x20 feet. Characters underwater find that reefs offer many hiding places; the encounter distance is only 1d8xl0 feet.
Ice Floes
Polar waters are often covered with ice of varying thickness, ranging from loose ice floes to dense pack ice so thick that pressure ridges hundreds of feet high can build up as huge ice masses move against each other.
Ice floes are dangerous to cross on foot but offer less obstruction to swimmers, who can simply dive under the ice cover. However, swimmers who must surface to breathe can become trapped and drown beneath ice too thick to break through.
Ice floes come in two varieties. A loose floe is the thinner (and more dangerous) of the two, with large stretches of open water. loose floes are found early or late in the season, when the pack ice is just beginning to form or has mostly melted off. Pack ice is much thicker. It's safer for travel on foot, but impenetrable for ships or air-breathing swimmers.
| Loose Floe | Pack Ice | |
| Crevasse | - | 5% |
| Floe, thin | 10% | - |
| Floe, thick | 15% | 10% |
| Ice Sheet | 40% | 50% |
| Lead | 20% | 15% |
| Pressure Ridge | - | 15% |
| Thin Ice | 15% | 5% |
Crevasse: These irregular cracks in pack ice are caused by ocean currents and shifting winds. A typical crevasse is anywhere from 30 to 300 feet long, 1d4x10 feet deep (deep enough to reach the water below), and 5d6 feet wide. A character falling into a crevasse drops into the freezing water at the bottom (see Hypothermia) and must make a DC 15 Swim check to tread water or move. In addition, the steep, slick sides of the crevasse offer little opportunity to climb out of the water unaided (Climb DC 30).
Some crevasses are hidden by thin crusts of snow; a character approaching a hidden crevasse is entitled to a DC 20 Spot or Survival check to notice the crevasse before stepping into it, although running or charging characters do not get to make this check.
Floe: A floe is an area of small floating bergs and water. They are normally 1d6 squares across but can extend for hundreds of feet. Any creature in the water is subject to hypothermia and must succeed on a DC 15 Swim check to tread water or move.
Each round, there is a 50% chance that a character in the water at the surface is struck by a piece of floating ice. Treat this as a slam attack (+5 melee, 1d2 damage). In a thick floe, this attack is at +10 melee, dealing 2d6 points of damage.
Swimmers at the surface must spend 2 squares of movement for each floe square they enter in a thin floe, or 4 squares of movement for each square in a thick floe.
Characters can attempt to cross a floe on foot, but it is extremely difficult. A character must succeed on a DC 25 Balance check to enter a square of a floe on foot; on a failure, he or she falls in the water. Thick floes are a little easier to walk across (DC 15 Balance check). Each square costs 2 squares of movement, and running or charging is impossible. The DC of Tumble checks increases by 20.
Ice Sheet: The ground consists of uneven, snow-covered ice. It costs 2 squares of movement to enter a square covered by an ice sheet, and the DC of Balance and Tumble checks increases by 5. A DC 10 Balance check is required to run or charge across an ice sheet.
Ice sheets are anywhere from 3 to 30 feet thick, although they can be much thicker around pressure ridges.
Extremely powerful swimmers (characters with a Swim speed) can attempt a DC 30 Strength check to break through an ice sheet from underneath. This would also apply to a walker who is standing on the bottom within reach of the ice sheet.
Lead: Areas of ice-free water in ice floes or pack ice are called leads. A small lead can be miles long and average 2d8x10 feet in width.
Pressure Ridges: Winds and currents sometimes cause ice sheets to crumple up, forming jagged hills of vertical ice 1d10x10 feet high, and twice that deep below the ice sheet. Pressure ridges normally run for many miles and are generally twice as wide as they are tall. A pressure ridge square is considered to be a steep slope and difficult terrain, costing 4 squares of movement to enter. The DC of Balance and Tumble checks increases by 10; it is impossible to run or charge on a pressure ridge.
Thin Ice: Thin ice is similar to an ice sheet, but it is only a few inches thick. A Medium creature that ends its move on a square of thin ice must succeed on a DC 10 Balance check or break through. A large creature that enters a square of thin ice must succeed on a DC 20 Balance check or break through, and Huge or larger creatures break through automatically.
If a creature breaks through thin ice, it creates a patch of open water 1 square larger than its own space on all sides - so a Medium creature is in the center of a patch of open water 3 squares wide. The water is freezing cold (see Hypothermia). In addition, climbing out of the water onto the ice is difficult; a creature trying to climb back on top of a square of thin ice must succeed on another Balance check at the same DC, or the square it was climbing onto breaks as well.
Powerful swimmers (Str 12 or more) can attempt to break thin ice from underneath.
Stealth and Detection in an Ice Floe: loose floes tend to be flat and open; the maximum distance at which a Spot check to detect the nearby presence of others can succeed is 6d6x20 feet. Pack ice features more broken terrain, and the distance drops to 3d6x10 feet.
Underwater, ice formations break up lines of sight and offer plenty of cover and concealment. The encounter distance for swimmers is 1d8x10 feet.
Open Water
The defining characteristic of an encounter in open water is the lack of terrain features. However, the ocean is not completely uniform. A swimmer sees the bright, dazzling patterns of the surface overhead and the steadily increasing gloom of the deeps underneath. These features provide creatures adapted to this environment with a background against which they can attempt to Hide. In order to use the darkness below or brightness above for concealment, a creature must be within 20 feet of the surface and above the observer, or at least 80 feet deep and below the observer.
The open ocean can be thousands of feet deep, but in relatively shallow waters (anywhere within 1 to 100 miles of shore, depending on where you are) the bottom is no more than a few hundred feet down (4d12x10 feet). The seafloor in open water generally consists of sand or soft muck, as featureless as the flattest prairie on land.
Stealth and Detection in Open Water: The maximum distance at which a Spot check to detect the nearby presence of others can succeed is 4d8x10 feet. Unless a character can get above or below an opponent, there is little concealment to be found.
Sargasso
In some seas, gigantic mats of floating seaweed grow so dense that adventurous (or desperate) travelers can attempt to cross them on foot. The mass of stinking, rotting seaweed often attracts monstrous scavengers of the worst sort (lacedons, monstrous crabs of all sizes, and the like), and sargasso can close in and entrap ships so thoroughly that escape becomes impossible.
Sargasso comes in two varieties: light and heavy.
| Light | Heavy | |
| Derelict | 5% | 10% |
| Mat, heavy | 15% | 60% |
| Mat, light | 50% | 20% |
| Pass | 30% | 10% |
Derelict: Ships entrapped in a sargasso can never escape. A derelict is a rotting hulk of a ship fouled with slime and seaweed, floating amid the densest sargasso mats. A typical derelict is a ship (cog, caravel, or launch), often in bad shape. Derelicts normally stand at least 10 to 20 feet above the sea level, and so they serve as high ground on the otherwise flat and boggy surface.
Mat, Heavy: Characters must spend 2 squares of movement in order to enter a square of heavy sargasso mat, and the DC of Tumble checks increases by 5. The mat is about 10 feet thick, and for 50 feet below that the seaweed impedes swimmers, who must spend 2 squares of movement to enter a square of heavy mat.
A Large creature that ends its move on a square of light mat must succeed on a DC 15 Balance check or break through. Huge or larger creatures break through automatically.
Mat, light: light sargasso is quite difficult to walk on. Characters must spend 4 squares of movement in order to enter a square of light sargasso mat; running and charging are impossible. The mat is about 5 feet thick, and for 20 feet below that dense tangles of seaweed impede swimmers, who must spend 2 squares of movement to enter a square of light mat.
A Medium creature that ends its move on a square of light mat must succeed on a DC 15 Balance check or break through. A large creature that enters a square of light mat must succeed on a DC 25 Balance check or break through. Huge or larger creatures break through automatically. If a creature breaks through light mat, it creates a patch of open water equal to its space. In addition, climbing out of the water onto the mat again is difficult; a creature trying to climb back on top of a square of light mat must succeed on another Balance check at the same DC, or it fails to climb up out of the water.
Pass: A pass is a stretch of open water in a sargasso. Characters walking atop a sargasso mat must swim to cross passes, while characters swimming through a sargasso find that passes permit them to pass through the seaweed without going around or over it.
Passes are normally 1d4x10 feet wide and meander randomly among the floating mats.
Stealth and Detection in a Sargasso: Characters on top of the sargasso can spot others at a distance of 3d6x20 feet. Underwater, the maximum distance at which a Spot check to detect the nearby presence of others can succeed is 1d8x10 feet due to the heavy cover provided by the seaweed mat.
Kelp Bed
Colder waters often hold great forests of kelp or similar varieties of seaweed along the coasts. Dense kelp can hide enemies and slow movement. A kelp bed is normally significant only in underwater encounters.
| Kelp bed | 50% |
| Rock reef | 20% |
| Sandy bottom | 30% |
Kelp: A square of kelp costs 2 squares of movement to enter. Any creature in a square of kelp has concealment; a creature more than 1 square away in kelp has total concealment.
A kelp bed is generally 2d8 squares wide and rises 1d8x10 feet from the seafloor; some can extend for hundreds of yards.
Rock Reef: These areas are simply obstacles underwater, a mass of submerged stone often heavily overgrown with anemones, barnacles, or other such creatures. A rock reef can serve as a wall or steep slope underwater, although swimmers can easily go around or over it.
Sandy Bottom: A sandy bottom offers no hazards or obstructions to swimmers but tends to break up patches of kelp and provide easy channels or trails through dense kelp beds.
Stealth and Detection in a Kelp Bed: Due to the heavy cover provided by this giant seaweed, the maximum distance at which a Spot check to detect the nearby presence of others can succeed is 1d8x10 feet.
Characters on the surface are completely above the kelp and can spot others who are also on the surface at a distance of 3d6x20 feet.
Ship's Deck
Many fights in which player characters are involved take place on the decks of a ship - their own, or one they've succeeded in boarding. A ship's decks tend to be cluttered and can be rendered slippery by blood or seawater, but since ships are essentially designed to be places where humans and humanoids can move about and work, they make for comparatively safe and secure footing.
Small ships are Gargantuan or smaller in size. Large ships are Colossal.
A fight on board a ship of any size can be drastically altered by the current weather conditions. These conditions apply to the whole ship, not just a few squares of it.
Heeling or listing: A ship can list from running aground or from flooding below decks. A heeling ship is a ship that is listing to one side from the effects of its maneuvers - a rapid turn at high speed, or a sailing ship lying somewhat on its side as it runs across or before strong wind. A mild list has the same effect as a gradual slope; there is no effect on movement, but characters gain a +1 bonus on melee attacks against foes downhill from them. A severe list is the same as a steep slope. Characters moving uphill must spend 2 squares of movement for each square of steep slope. Characters running or charging downhill must succeed on a DC 10 Balance check upon entering the first steep slope square. Characters who fail this check stumble and must end their movement 1d2x5 feet later. Characters who fail by 5 or more fall prone in the square where they end their movement. A severe heel or list increases the DC of Tumble checks by 2.
Heavy Rolls: Ships in heavy weather can take violent rolls, rocking precipitously from side to side. Heavy rolls have the same effect as a severe list, except from round to round the high side and low side reverse, with a round of level deck in between (round 1: starboard high; round 2: even; round 3: starboard low; round 4: even; round 5: starboard high again, and so on).
Green Water: Ships in heavy seas can take green water over the bows or sides - powerful rushes of surf that wash across the deck, threatening to knock down or carry away anyone on deck.
A light surge of green water lasts for 1 round and repeats every 2d4 rounds. A light surge is about 1 foot in depth. It costs 2 squares of movement to enter a square of light green water, and the DC of Tumble checks in such a square increases by 2. Any creature that begins its turn in or enters a square of light green water must succeed on a DC 6 Strength check or Balance check, or fall prone. Characters who fall prone are washed 1d4 squares in the direction of the surge; if this would wash them over the side, they are entitled to a DC 11 Reflex save to catch themselves at the rail before going over. A heavy surge consists of violently surging water about 4 feet in depth. It costs 4 squares of movement to enter a square of heavy surge. Tumbling is impossible in a heavy surge. Any creature that begins its turn in or enters a square of heavy surge must succeed on a DC 12 Strength check or Balance check, or fall prone. Characters who fall prone are washed 2d6 squares in the direction of the surge; if this would wash them over the side, they are entitled to a DC 17 Reflex save to catch themselves at the rail before going over.
| Small | Large | |
| Deck | 40% | 40% |
| Deck, cluttered | 10% | 10% |
| Deck, raised | 10% | 20% |
| Deck, slippery | 5% | 5% |
| Hatch | 10% | 10% |
| Mast | 5% | 5% |
| Water | 20% | 10% |
Deck: Most squares of the ship are unobstructed deck, imposing no penalties to movement or combat (unless the ship is listing, rolling, or taking green water over the deck).
Deck, Cluttered: Any square obstructed with various nautical gear - capstans, coils of line or chain, casks, cargo, small boats, stays, or rigging is considered cluttered. Cluttered deck provides cover and increases the DC of Tumble and Move Silently checks by 2.
Deck, Raised: Many ships feature raised decks at the forecastle and stern. The raised deck is normally 8 to 10 feet above the main deck, reached by a set of short, steep steps.
Deck, Slippery: A deck wet from ocean spray, ice, blood, or for some other reason becomes slippery. It costs 2 squares of movement to enter a square of slippery deck, and the DC of Balance and Tumble checks increases by 5. A DC 10 Balance check is required to run or charge over slippery deck.
Hatch: A hatch is an opening in the deck leading below. A small hatch has a ladder (a short, steep staircase really) and is 1 square across, while a cargo hatch is 2 squares wide and usually doesn't have a ladder.
Mast: A ship's mast is anywhere from 1 to 3 feet thick at the deck level, depending on the size of the ship. A creature standing in the same square as a mast gains a +2 bonus to AC and a +1 bonus on Reflex saves (these bonuses don't stack with cover bonuses from other sources). The presence of a mast doesn't otherwise affect a creatures fighting space, because it's assumed that the creature is using the mast to its advantage. A typical mast has AC 4, hardness 5, and 150 hp. A DC 20 Climb check is needed to climb a mast.
Water: Any square that isn't actually part of the ship is water. Vessels of Huge size or smaller have decks that are no more than 5 feet above the water. Gargantuan vessels have decks 10 feet above the water. Colossal vessels have decks 15 to 25 feet above the water.
Stealth and Detection on Deck: Characters on the deck of a ship automatically spot other characters on deck unless the other character is hiding. The deck of a ship provides plenty of both cover and concealment, so hiding is not all that difficult. Characters encountering creatures in the water are entitled to Spot checks to notice the presence of creatures at or near the surface at a distance of 3d6x10 feet (although very large creatures can be spotted considerably farther away).
Marine Adventure Ideas
- A sahuagin warband terrorizes a coastal town, searching for a rogue malenti.
- An evil storm giant demands tribute from passing ships.
- Fishermen discover a sunken city haunted by undead merfolk controlled by amphibious illithids.
- A sea cave guarded by ixitxachitl hides the temple of an evil god.
- Sightings of a ghost ship prove to be omens of shipwreck and disaster.
- The heroes' ship is becalmed in a gigantic sargasso haunted by lacedons and monstrous crabs.
- Slavers carry captives back to a mysterious island stronghold.
- A sunken ship is rumored to have been carrying a powerful magical artifact.
- Aboleths seek to capture and dominate wizards in accordance with a diabolical scheme.
- A merfolk sage holds the answer to a puzzling mystery.
- An aventi knight of the pearl warns that a sea witch plans to devastate shipping lanes between two cities.
- A mysterious storm batters a port for months without abating.
- Sailors are lured to a miragelike island; only their abandoned ships beached on the sands remain to hint at their fate.
- A daring captain seeks a crew to sail with her on a risky voyage through icebound northern seas.
- A dark, still lake in the jungle is said to hold tons of gold sacrificed to a strange lake god.
- A vengeful sea demon swears vengeance on the descendants of a hero who defeated her long ago.
- Terrestrially adapted aquatic creatures are beginning to overrun a coastal region; the local lord suspects a wavekeeper of the green waters is responsible.
- A darfellan leviathan hunter seeks companions in his quest to hunt a mosasaur that is terrorizing the region.
- A band of aquatic elves is trying to find a malenti spy who has taken refuge ashore; they need help finding her in the unfamiliar terrestrial surroundings.
- A shipful of hadozee privateers need help fulfilling their vow to hunt down a notorious scarlet corsair.