Marine mammals live in and obtain their food from the sea. But, just like other mammals, marine mammals are warm-blooded; they have lungs and they breathe air. The give birth to living young that are dependent on milk from
developed to catch their own food. The structure of a marine mammal is generally the same as that of land mammals; the internal organs and main elements of the skeleton are the same. Whales have come furthest in their adaptation to a life in water, followed by sea cows and seals. Whales and sea cows spend their entire lives in water and also give birth to their young there. They have become specialised in swimming and have totally lost the ability to move around on land. Seals, on the other hand, give birth to their young on land or drift ice. This means that they still need to be able to move around on land.