A dolphin's fluke is a paired, triangular structure at the end of the dolphin's tail. It is the main means of propelling the animal forward, while other fins are used for steering.
The fluke is made up of collagen and positioned horizontally, so when the dolphin moves its tail up and down, the flukes will strike the water. The flukes are powered by muscles attached to the back and belly. They are strong enough to allow the animal to leap clear of the water or disorient fish with a slap. Their broad, flat surface also aids in thermoregulation, providing a large surface area for body heat to be released.