As large semi-aquatic marine mammals, seals, sea lions, and walrus are particularly important for many coastal cultures. Harvested both on land and in water, seals, sea lions, and walrus are mainly used for their meat, fat blubber, and skin, but nearly all parts are used.
Seals, sea lions, and walrus are large, marine mammal carnivores that feed at sea, but breed on land or on ice. They are all part of the pinnipeds, or fin-footed carnivores, and all have paddle-like fore and hind limbs, a large streamlined body, and a thick fat blubber layer under their skin. Pinnipeds are divided into three families: 1) fur seals and sea lions, 2) true or earless seals, and 3) walruses (of which the walrus is the only living species). Fur seals and sea lions are distinguished from true seals by their external ear flaps, a thick fur coat, and their ability to rotate their hind flippers forward to walk on them, while true seals can only crawl by undulating their body. True seals have lost much of their dense fur, replaced by thicker fat blubber to compensate. True seals have contrasting colour patterns and undergo an annual molt, while fur seals and sea lions have more uniform colouration and renew their fur gradually throughout the year.
Reference
Berta A: Pinnipedia, overview. In: Encyclopedia of marine mammals. edn. Edited by Perrin WF, Wursig B, Thewissen JGM. San Diego: Academix Press; 2002: 903-911.