Otters are playful ocean mammals that belong to the Mustelidae family, which also includes weasels, badgers, and wolverines. They have long, slim bodies with short legs, webbed feet, and a thick fur coat that helps them stay warm in cold water. They are known for their playful behavior, such as sliding down muddy banks and playing with rocks and sticks. They are also very social animals, living in groups of up to 15 individuals.