Seals, sea lions and walruses are strong, agile swimmers but, unlike cetaceans, they can live on land. Once ashore they tend to waddle around awkwardly. In spring and summer, thousands of seals crowd together in vast colonies to breed. Killer whales and other toothed whales are fearsome hunters, feeding on seals, porpoises and penguins, as well as fish. They will even attack young or injured blue whales, the biggest creatures that ever lived.
Dolphins are exceptionally friendly, playful and intelligent creatures.
They are believed to talk to each other by an elaborate language of clicking sounds. Seals have a streamlined shape which enables them to swim very fast. But on land, where they breed, they are very slow. Most seals eat fish, squid and krill, but the leopard seal will eat penguins and other seals. Walruses live on beaches near shallow waters at the edge of the polar ice in the Arctic.