Natural environments and the animals that live in them can be categorized as aquatic (water) or terrestrial (land). Aquatic animals may breathe air or extract oxygen that dissolved in water through specialized organs called gills, or directly through the skin. Examples are Whales and Dolphins. Natural environments and the animals that live in them can be categorized as aquatic (water) or terrestrial (land). Terrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, spiders), as compared with aquatic animals, which live predominantly or entirely in the water (e.g., fish, lobsters, octopuses), or amphibians.