harks do sleep, but not in the same way that humans do. Sharks’ sleep can be divided into a less active and deep slumber. Sharks that can’t stop swimming move into a rest period characterized by reduced activity. On the other hand, sharks with spiracles can fall asleep quickly since they can stop swimming if they want to.
Whales have tail fins. Whale tails, however, differ significantly from the tails of other fish, including sharks. A whale’s tail has two lobes called flukes that move up and down rather than side by side and are separated by a deep cleft. Furthermore, rather than bones, the flukes are composed of dense, fibrous connective tissue.