Whale

Whales are mammals, but they live in sea. They breathe air, but they cannot survive on land. Sometypes of whale are very large indeed. Blue whales, for example, can grow to more than 30 meters in length. They are the largest animal that have lived on earth.
At a glance whales look rather like fish. However, there are some important differences in their external structures. Whales have tails that are board, flat and horizontal. These tails function as paddles. They also have single nostrils on top of their large, board heads.
A whale's skin is smooth and shiny. Beneath the skin there is a layer of fat or blubber. The fat is up to 30 cm in thickness. This fat keeps heat and fluids so that it can live in cold waters.