Beavers are large rodents and have an ungainly waddle on land but they are graceful in the water, where they use their large, webbed rear feet like swimming fins, and their paddle shaped tails like rudders. They can swim at speeds up to 5 miles per hour and can remain underwater for 15 minutes without surfacing.

They have a set of transparent eyelids (nictitating membrane/third eyelid) that function like goggles. Their ears and nostrils have valves that close to prevent water entry and they have fur lined lips that form a seal behind their teeth that allows them to hold their breath while they peel, cut or carry branches under water. Their fur is oily and waterproof.