It should be no surprise that otters are great swimmers. But how great are they?
Otters have a powerful, somewhat flattened tail perfect for propelling themselves through the water. They have webbing between their toes as well. They can close their nostrils and ears to keep out water, and have sensitive whiskers to feel out prey even in the murkiest water. Otters can hold their breath for 3-4 minutes at a time while they swim, and can swim at speeds of 6.8 miles per hour.
When river otters are born, they actually don't know how to swim. Despite being born in the water, they still need to be taught to swim by mom.