An otter is an aquatic mammal that is known to be a shellfish eater. They have webbed feet and a streamlined body that helps them swim quickly and efficiently. Otters are found in many parts of the world, including North America, Europe, Asia, and Africa. They feed on a variety of shellfish, such as clams, mussels, and crabs. Otters are also known to eat other types of aquatic animals, such as fish, frogs, and crayfish.