Aquatic

Aquatic relates to any organism or plant species that requires an underwater environment in order to survive. On Earth, most aquatic species of animals are marine-based, mostly species of fish, but may also include other life forms as well. There are many fictional races, both terrestrial and alien, who are aquatic beings. One of the common traits among aquatic life forms is aquatic respiration, which enables them to process oxygen from water and excrete carbon dioxide for purposes of respiration. Another benefit amongst some amphibious races is environmental adaptation.

Marvel Comics
In Marvel Comics continuity, the most prominent aquatic race are the Atlanteans, who are blue-skinned marine humanoids that live beneath the sea. They are an off-shoot race of their cousins, the Lemurians, whose ancestry is also tied to that of the Deviants. There are many aquatic monster and animals that live beneath the sea, who may also be able to trace their genetic origins to the Deviants.

DC Comics
In DC Comics continuity, the most prominent aquatic race are also called Atlanteans. Unlike their Marvel Comics counterparts, the DCU Atlanteans largely resemble baseline humans, and are only distinguished by fins on the calves of their legs.

Star Wars
In the Expanded Universe of the Star Wars multimedia franchise, there are many different aquatic races. The films themselves have presented races such as the Aqualish, the Quarrans, the Mon Calamari and the Nautolans.