Otters have long, slim bodies and relatively short limbs, with webbed paws. Most have sharp claws on their feet, and all have long muscular tails.
They have a very soft underfur which is protected by their outer layer of long guard hair. This traps a layer of air, and keeps them dry and warm under water.
Most otters have fish as the primary item in their diet, supplemented by frogs, crayfish and crabs. Some are expert at opening shellfish, and others will take any available small mammals or birds.
Otters are playful animals, for example sliding repeatedly down snowy slopes, apparently from sheer enjoyment.