Plane of Water
It is an ocean without a surface. It is domain of current and wave. It is a bottomless depth. Water is one of the four elements and two energies that make up the known universe and therefore of great interest to cosmologists. This plane was abundant with life: native creatures born of the elemental nature of the plane itself, sentient water-breathing peoples, and most every species of aquatic life that could survive after being sucked through a vortex from their plane of origin. Elemental vortices could occur wherever a high concentration or nearly pure form of an element was found, and could be temporary or permanent. Vortices to the Plane of Water could often be found in the deepest parts of the seas and oceans, in clear underground lakes, or as surface whirlpools in any large body of water. There was no deep or shallow, no dark depths nor wavy surface, just an endless ocean that felt as if you were submerged several feet (say a couple meters) in any body of water on the Prime Material Plane. There was no sun, yet the water itself seemed to glow dimly with a bluish green luminescence. Volumes of water at any temperature and salinity could be found if you knew where to look or had a guide. Impurities such as bubbles of air, chunks of earth, and even short-lived balls of fire could be found floating about due to elemental vortices or the workings of powerful beings. Habitats and settlements typically formed near sources of food and shelter, or near portals and vortices to facilitate trade. Supporting the teeming life of this plane were the corals and plants that made their way here and found purchase. Huge drifting three-dimensional reefs and loose spheres of freshwater grasses, kelp, and seaweed were home to myriad species and were fertile fishing spots. Travelers had to keep in mind that large predators knew of these fishing grounds also, or else they might discover just how bite-sized they actually were. Just like a Prime ocean, the Elemental Plane of Water seemed to have no limit on how large some creatures could be as giant squid, aboleth, and kraken were known to prowl the plane. Small creatures could be deadly too, with poisonous spines or barbed tails. The smallest of them all was perhaps the deadliest: algae that formed the infamous "red tide". Exposure of the eyes or lungs to the red tide caused a blinding sickness as virulent as any disease. If the Plane of Water had any weather, it was the currents, whirlpools, tidal bores, and flows of ice, steam, or silt that could inconvenience a traveler or be a deadly surprise. Usually invisible, currents could be strong enough to pull visitors off in some direction for long distances before they were able to exit the current. Tidal bores were the most dangerous currents, hitting like a thrown boulder and carrying the unlucky creature away for miles (kilometers). Whirlpools were caused by countervailing currents that sucked everything in a tightening spiral, some of which lead to vortices to other planes. Ice and silt flows were fairly easy to spot before encountering, but steam flows were nearly undetectable and could cause nasty burns or boil the flesh from your bones.