The skin of whales is usually black, gray, black and white, or all white. The surface of the skin is smooth.
Whales have the general bow shape of a fish, though in some whales the head is greatly enlarged.
In a special adaptation to sea life, the hind limbs of whales have vanished completely. The forelimbs are made up of the same bones as those of other mammals but are shortened. The fingers have been greatly lengthened and enclosed in mittens of flesh, which form the flippers. Flippers are used not for swimming but for steering. The powerful tail ends in a pair of lobes, or flukes, which extend horizontally on either side instead of vertically, as do the fins of a fish's tail.