An otter is a swimming mammal that belongs to the Mustelidae family, which also includes weasels, badgers, and ferrets. Otters are found in many parts of the world, including Europe, Asia, and North America. They are semi-aquatic animals, spending much of their time in the water and on land. Otters have webbed feet and a thick fur coat that helps them stay warm and dry while swimming. They are also known for their playful behavior and intelligence.