The sea otter is a mammal belonging to the Carnivorous Order, Weasel Family, and Sea Otter genus. Unlike other marine mammals, sea otters do not have a subcutaneous fat layer for warmth. The sea otter is a famous fur beast, and its fur serves to isolate and keep warm. The common name for sea otter fur is sea dragon fur, which is the most valuable type of fur, especially the fur in the center of the back, which is four times denser than mink fur, known as the "king of fur". Sea otters are the smallest marine mammals. The body is cylindrical, with a length of 1.40-1.48 meters and a weight of 32.5-45 kilograms. The flat tail accounts for about a quarter of the body length. The head is short and wide.