Flipper
From Simple English Wikipedia, the free encyclopedia

A flipper of a Humpback Whale

Swimmer's flippers
A flipper is a special kind of limb that is shaped like a paddle for moving through water that aquatic animals, (animals that live in water) such as whales and seals have. The flipper of a fish is called a fin.
It can also be an item worn on the foot to help people swim more easily.