The Elemental Plane of Water

It is an ocean without a surface.
It is domain of current and wave.
It is a bottomless depth.
The Elemental Plane of Water is a sea without a floor or a surface, an entirely fluid environment lit by a diffuse glow. It is one of the more hospitable of the Physical Planes once a traveler gets past the problem of breathing the local medium. The eternal oceans of this plane vary between ice cold and boiling hot, between saline and fresh. They are perpetually in motion, wracked by currents and tides. The plane's permanent settlements form around bits of flotsam and jetsam suspended within this endless liquid. Even these settlements drift on the tides of the Elemental Plane of Water.

Creatures of the Plane of Water

The Elemental Plane of Water is relatively benign for a Physical plane and is home to a large number of native elementals, water-breathing outsiders, and creatures from other planes that can survive in its watery seas.
Elementals are discrete and separate manifestations of the plane itself, granted sentience and mobility from magic or natural forces. These include the water elementals summoned by spellcasters and elemental versions of Material plane creatures. Such creatures tend to be at least semiliquid and mimic seagoing beasts and monsters of the Material Plane.
Many water-breathing outsiders also make the Elemental Plane of Water their home. These include such transient beasts as the tojanida and the mephit, as well as more settled groups such as marid genies. In general, water-breathing outsiders found on the Elemental Plane of Water tend to be playful and cruel, not hesitating to torment (and drown) interplanar visitors who rely on magic spells or items to survive on their plane.
Finally, water-breathing creatures from other planes may be found on the Elemental Plane of Water. Fish, crustaceans, cephalopods and most sea-dwellers live on this plane, but not air-breathing ocean-dwellers such as whales and dolphins. The Elemental Plane of Water is hospitable to both freshwater and saltwater species, though each type has its own regions to inhabit. Monstrous aquatic creatures such as the kraken and aboleth may be found here as well.
Portals seem to be common between the Elemental Plane of Water and oceans on the Material Plane, and rarer portals connect to large bodies of water on other planes. Marids in particular make use of the vortices, and settlements of these creatures are usually found near permanent portals.
Natives of the Elemental Plane of Water speak Aquan, a flowing, subtle language filled with double meanings and hidden puns. Those dealing with other planes speak other languages to facilitate their dealings: Common, Infernal, Abyssal, and Celestial are frequent choices.

Locations and Features of the Plane of Water

The Elemental Plane of Water holds but one great immediate danger, and that is the fluid nature of the plane itself. Unless a traveler can breathe water or has no need to breathe, any visit to the Elemental Plane of Water must be brief. Those unable to breathe must hold their breath while on the plane and run the risk of drowning.
Creatures made of fire (such as fire elementals) take 1d10 points of damage each round on the Elemental Plane of Water, because it has the water-dominant trait. Creatures with the fire subtype are very uncomfortable on the plane.
A great difference between the Elemental Plane of Water and other watery domains is a lack of pressure. In Material Plane oceans (and some others), the pressure of the water increases with depth. The water pressure can grow strong enough on the Material Plane to crush the life out of creatures and bend steel. But the pressure on the Elemental Plane of Water is no worse than a just few feet underwater in a Material Plane ocean, so there are no dire consequences.
Long-term survival on the Elemental Plane of Water is fairly easy. Obtaining water is obviously not a problem, though its purity and salinity may pose some difficulties in specific areas. The abundance of sea life in the plane is enough to satisfy any traveler with a taste for fish. A vague, dim glow that issues from all sides illuminates the seas of the Elemental Plane of Water. This glow gives everything a blue-green aura, but limits clear vision. Normal vision, including darkvision, is limited to 60 feet. Clouds of silt, algae, and other detritus may limit sight even further.

Hot Spots and Ice Pockets

The bulk of the Elemental Plane of Water is within a comfortable temperature range, like ocean temperatures in warm or temperate coastlines on the Material Plane. There is no inherent temperature danger to travelers in areas that are within this range.
However, in spots the temperature changes dramatically. Hot spots raise nearby water to the boiling point, dealing 1d10 points of fire damage to those caught too close. The warmest of hot spots may have vortices to the Elemental Plane of Fire, and in these regions flames may briefly flicker before being inundated by the endless water.
Similarly, cold regions drift on the currents, some so cold that they sap the life out of those caught within. Unless otherwise protected, creatures take 1d6 points of cold subdual damage per minute within such an area. At the heart of these regions solid ice may be found, and there wander such cold-loving creatures as ice paraelementals. Hot spots and ice pockets are usually no smaller than 300 feet across, and ones of a mile or more across have been reported. Movement is unaffected within these regions.
Such areas are hard to spot visibly, but the temperature changes around their edges are gradual. Creatures usually know of the approach of a hot spot or cold pocket 1d10 minutes before it starts dealing damage. Under normal situations, this is sufficient time to swim for more moderate waters.

Currents, Whirlpools, and Bores

Most of the Elemental Plane of Water swirls with a dizzying tangle of currents, moving the various fixed locations around with slow ease. Settled areas are aware of the course and heading of other settlements, though the distances may become insurmountable and communities lost to each other through the eternal sea.
Some currents are stronger than others. Strong currents may drag travelers in a particular direction at up to 120 feet per minute (roll 2d6×10 to determine the current's strength in feet per minute). Travelers must be able to move faster than the current to make progress in the opposite direction.
Some currents pose a physical danger. Whirlpools are localized areas formed by counter-flowing currents that suck everything within 1d10×30 feet into a tightening spiral. Those caught within a whirlpool must make a Swim check (DC 15) or take 1d6 points of damage from the buffeting current. Make this check every round. Those caught in a whirlpool can escape it with a second successful Swim check (DC 15) or automatically after 2d6 rounds. Some 30% of whirlpools have vortices at their bases, and creatures sucked in are ejected on some other plane, either on the Material Plane or on another plane that has an area with the water-dominant trait. Make a Reflex save (DC 19) for anyone caught in the whirlpool for each round after the sixth to avoid being sucked into the vortex. The DM determines where the vortex leads.
The most dangerous currents are tidal bores, great fluid avalanches that course through the plane, spreading destruction in their wake. Anyone caught in a tidal bore must succeed at a Swim check (DC 20) or take 2d10 points of damage. In any event, creatures hit by a tidal bore are dragged miles away by the force of the water.

Red Tides

A dangerous contagion has infected patches of water where red tides occur. Red tides range from a mere 60 feet across to areas large enough to comprise entire seas of pestilence. Those who inhale the deadly water or whose unprotected eyes are exposed to it may fall victim to blinding sickness. Unlike with most diseases, the initial Fortitude save to avoid infection must be made each minute a character remains in a red tide.

Weeds and Coral

Balls of seaweed and coral float through the Elemental Plane of Water, growing in all directions equally and resembling planets of living plant life. These spherical beds are often the lairs of outsiders native to the plane. The waters around weed and coral spheres frequently have excellent fishing grounds, so sometimes marids build outposts nearby.

Marid Communities

Marids are a fiercely independent race, so the “marid empire” on the Elemental Plane of Water is really a large collection of semi-independent strongholds, all of which swear fealty in varying degrees to the padishah of the marid. Often that degree of fealty is determined by the proximity of the stronghold to the Citadel of Ten Thousand Pearls or the presence of agents of the padishah. All marids claim nobility of some kind, and the plane is filled with shahs, atabegs, and mufti.
A typical marid stronghold is tied to some type of jetsam, usually a bit of solid matter or even a weed bed. Usually 2d10 marids are found in such a community, with a variety of elemental servants and jann, as well as mortals who have lost bets, sought favors, been chosen as favorites, or otherwise wound up enslaved by the (relatively) benign marids. They have little use for evil creatures, even those that breathe water, and marids are frequently at war with the evil denizens of the Elemental Plane of Water.
The Citadel of Ten Thousand Pearls is the greatest of marid communities and the seat of the Coral Throne. From this court emanates the wise rulership of the Great Padishah of the Marid, the Keeper of the Empire, the Pearl of the Sea, the Parent of the Waves, the Maharaja of the Oceans, Emir of All Currents, and so forth. This citadel, set atop a free-floating coral reef, is bedecked with all manner of towers and halls carved from living shell and ringed with luminous, glowing pearls. About two hundred marids make the citadel their home, all of them nobility. Each marid has a set of personal servants, bringing the non-marid population of the citadel to about a thousand. The court of the great padishah is filled with intrigue and espionage because each marid has the heartfelt belief that he or she truly deserves to sit atop the Coral Throne.
Assassinations are common, as are palace revolutions and exiles. The marids are individually the most powerful of genies, but their strong wills and high opinions of themselves themselves prevent them from banding permanently under any one leader.

City of Glass

For travelers with less of a taste for palace intrigue, the City of Glass is an ideal gathering spot on the Elemental Plane of Water (especially for travelers who breathe air). Located at a stable collection of portals to other planes (stable in that they do not move in relationship to each other), the City of Glass consists of a great sphere of unbreakable glass, half filled with water. Visitors enter the city through any number of openings along the water side, or through magical portals in the air-bubble half. Many buildings cross the boundary between air and water, there are buildings filled with water in the air half, and buildings equally stocked with air beneath the water's surface. By mutual agreement of the city's resident, “down” is toward the water half of the sphere.
The City of Glass is a cosmopolitan collection of traders, travelers, and expatriates from other planes. Its denizens are primarily from the aquatic races of the Material Plane, including merfolk, kuo-toas, lizardfolk, and sahuagin. It is ruled by a council of longtime residents, no two of whom may be of the same race. The city is a merchant's freeport and actively encourages trade. Mercanes may be found within its borders, along with marids, dao, and human traders. Several of its portals lead back to the Material Plane, and it is said that in secret places within the city, there are portals to other planes as well.
Historians note that the “unbreakable” glass of the dome has been broken in the past. Without definite gravity, however, the air remained more or less where it was. The city officials immediately repaired the rift and put to death the visitors whose errant spells were responsible for the break.

Traits

Subjective Directional Gravity: The gravity here works similar to that of the Elemental Plane of Air. But sinking or rising on the Elemental Plane of Water is slower (and less dangerous) than on the Elemental Plane of Air.
Normal Time.
Infinite Size.
Alterable Morphic.
Water-Dominant.
Mildly Neutral Aligned.
Enhanced Magic: Spells and spell-like abilities that use or create water are both extended and enlarged (as if the Extend Spell and Enlarge Spell had been used on them, but the spells don't require higher-level slots). A water breathing spell would thus last 4 hours per level, rather than 2 hours per level. Spells and spell-like abilities that are already extended or enlarged are unaffected by this benefit.
Impeded Magic: Spells and spell-like abilities with the fire descriptor are impeded. This includes spells of the Fire domain. These spells and spell-like abilities can still be used, but a successful Spellcraft check (DC 15 + level of the spell) must be made to do so.