Otters are freshwater mammals that belong to the Mustelidae family, which also includes weasels, badgers, and wolverines. They are semi-aquatic animals, meaning they spend part of their time in the water and part of their time on land. Otters have long, slim bodies with short legs and webbed feet, which help them swim quickly. They have thick fur that helps keep them warm in cold water and they have a layer of fat that helps them stay buoyant. Otters are carnivorous and feed mainly on fish, crustaceans, and mollusks.