River Otter - This mammal lives near and spends most of its time in water. The Otter is an expert swimmer and diver; however, they move rather awkwardly on land. Most River Otters weigh from 10 to 30 pounds. Its fur is brownish-gray to dark brown and it has a small, flattened head, a long thick neck and a thick tail that narrows to a point. Otters eat crayfish, crabs and fish. The otter is also well known for its playfulness.