Otters are semi-aquatic mammals that belong to the subfamily Lutrinae. They have thick fur that keeps them warm and dry in the water. Otters are playful and intelligent animals that enjoy sliding, diving, and swimming. They also like to rest on their backs, holding hands with their mates or family members to prevent drifting apart. Otters are found in many parts of the world, such as North America, Europe, Asia, and Africa. Some of the most common species are the sea otter, the river otter, the giant otter, and the Asian small-clawed otter.