Otters are playful sea animals that belong to the Mustelidae family, which also includes weasels, badgers, and wolverines. They are semi-aquatic mammals that live in rivers, lakes, and coastal areas. They have a thick fur coat that helps them stay warm in the water and they use their webbed feet to swim. They are known for their playful behavior, such as sliding down muddy banks, playing with rocks, and chasing each other.