Whales are sea living mammals.
They therefore breathe air but cannot survive on land. Some species are very large indeed and the blue whale, which can exceee 30m in length, is the largest animal to have lived on earth. Superficially, the whales looks rather like a fish, but there are important differences in its external structure; its tail consists of a pair of broad, flat horizontal paddles. It has a single nostril on top of its large broad head.
The skin is smooth and shiny and beneath it lies a layer of fat. This is up to 30cm in thickness and serves to conserve heat and body fluids.