While some species of sharks do need to swim constantly, this is not true for all sharks. Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest. Because gills constantly need water running over them to allow their owner to breathe. Sharks do not sleep like humans do, but instead have active and restful periods. Scientists believe that some species of shark never actually go into deep sleep. Instead, these aquatic hunters will power down, lazily drifting along.
I StumbledUpon this article where sharks are ranked 3rd on Countdown: Strangest Animal Sleeping Habits. I believe they earned their spot on that list. Check out which animal made number one! Pawnation
Personally, I think the sharks were robbed. What do you think?