Mammals are warm blooded animals that feed their young on milk. Mammals have adapted to a fantastic range of habitats. Look at the Desert Moles, who live their life in the desert. Look at Polar Bears who freeze their butts off on the ice floes. Look at the otters, both Sea and Fresh water. Look at pigs, mmmmm, Bacon. Look at porpoises, dolphins, manatee, whales, dugong, walrus and seal. The last seven all live in water. One thing a mammal needs is to breath oxygen. All mammals have internal lungs that require respiration.. Respiration exchanges the oxygen burned by the body, using carbohydrates, to produce carbon dioxide. Lungs and water do not mix as water is not the best medium for exchanging gases. Usually leads to drowning when a lung is full of water.. Man has a nose to breathe through as do all other mammals. The whale and porpoise has a blowhole locate roughly on the top of their heads. They have to breach or break the surface to breathe. Others, like the seals, just stick their noses out of the water and take a breath.