When slapped against the water, it serves as a sign of warning, but it can signal other emotions as well. When the beaver stands up on its hind legs to cut down a tree, the tail is like a fifth leg used for balance. The beaver is designed to swim and work under water. Its nose and ear valves close when the beaver is submerged. A beaver can cut and chew submerged wood without getting water in its mouth by drawing its loose lips tightly behind the protruding front teeth.
Water provides a refuge from enemies.
Beavers build canals to float and transport heavy objects such as branches and logs for food and construction. Food for winter use must be stored in underwater food caches. If the habitat does not have the necessary water level, beavers construct dams. Each dam is a little different. A beaver may work alone or with family members to build a dam, using piled logs and trees secured with mud, masses of plants, rocks, and sticks.