The sea otter (Enhydra lutris) is the heaviest member of the weasel family but among the smallest marine mammal. Native to the east coasts of North America, their primary form of insulation is an exceptionally thick coat of fur; for which they were hunted extenisvely until 1911, decimating populations.

Although it can walk on land, the sea otter lives mostly in the ocean where it inhabits offshore environments, diving to the sea floor to forage on marine invertebrates such as sea urchins, various molluscs, crustaceans, and some species of fish. Interestingly it makes use of rocks by holding in its paws to dislodge prey, and to smash open shells.