Otter is a common name for a carnivorous mammal in subfamily Lutrinae. The 13 extant otter species are all semiaquatic or aquatic, with diets based on fish and invertebrates. Otters have long, slim bodies and relatively short limbs with webbed paws. Most have sharp claws on their feet and all except the sea otter have long, muscular tails. The 13 species range in adult size from 0.6 to 1.8 m (2.0 to 5.9 ft) in length and 1 to 45 kg (2.2 to 99.2 lb) in weight. The Oriental small-clawed otter is the smallest otter species and the giant otter and sea otter are the largest. They have very soft, insulated underfur, which is protected by an outer layer of long guard hairs. This traps a layer of air which keeps them dry and warm underwater.