What is a marine mammal?

Marine mammals are mammals that have evolved to live in the ocean, ranging from polar oceans to tropical waters, and from the surf zone to the deep ocean more than a mile below the surface. They are warm-blooded, air-breathing vertebrates who spend a part or all of their lives in the ocean. While these mammals are marine, some also make use of land. These mammals have some special features that help them get around better than humans. They have streamlined bodies that help them swim fast in water, flippers or webbed feet to improve swimming, and a thick layer of fat known as blubber that keeps them warm in cold waters. They include species like whales, dolphins, seals, sea lions, manatees, and others.