Unlike the other members of the amphibious otter family, the sea otter (Enhydra lutris) lives the majority of its life in the water. The sea otter, the largest member of the weasel family, ranges along the Pacific coast from Alaska to California.

Nature has equipped the sea otter with many adaptations for a life in the ocean: tightly-packed water-repellant fur; a long, strong, and flexible body built for vigorous swimming; flipper-like hind feet and webbed paws to propel it through the water; and ears and nostrils that close underwater.

An adept underwater hunter, the sea otter has a very rapid metabolism and must eat frequently, often four times each day. Its stiff whiskers are sensitive to water turbulence and alert the otter to nearby prey, which it snatches in its strong jaws. An otter eats what is readily available and easy to catch, including fish, frogs, crayfish, and crabs. The sea otter's large, rounded molars are perfect for crushing sea urchins, abalone, and mussels, which it pries from rocks with its forepaws.

When it comes to handling objects, the versatile otter is a master of manipulation. Other than primates, otters are the only mammals that use tools in obtaining food. To dislodge abalone underwater, an otter grasps a stone between its forepaws and bangs it against the edge of an abalone shell. It may take three or more dives to successfully dislodge the tasty abalone from its shell. However, an otter may use the same stone over and over again.

Once it has obtained its catch, the sea otter brings its food to the surface. The otter places a stone on its chest and uses it as an anvil on which to open mussels, clams, and other shellfish. Food is carried to the surface in the otter's forepaws and the stone is placed in a flap of skin under its arm. The otter may roll in the sea between bites to clean itself of debris and keep its fur clean.

The fur coat which was perfect for a life at sea also nearly cost the species its life. The sea otter was hunted close to extinction for its pelt until it was protected by one of the first international endangered species agreements in 1911.