An
aquatic animal is an
animal, either
vertebrate or
invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called
gills, or directly through its skin.
Natural environments and the animals that live in them can be categorized as aquatic (water) or
terrestrial (land). Animals that move readily from water to land and vice versa are referred to as amphibians.