American Beaver

It has a large flat paddle-shaped tail and large, webbed hind feet reminiscent of a human diver's swimfins. The unwebbed front paws are smaller, with claws. The eyes are covered by a nictitating membrane which allows the beaver to see underwater. The nostrils and ears are sealed while submerged. A thick layer of fat under its skin insulates the beaver from its cold water environment.
The beaver's fur consists of long, coarse outer hairs and short, fine inner hairs. The fur has a range of colours but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur.