How do hammerhead sharks sleep while swimming?

One thing that all sharks have in common is the physiologic need for a constant flow of water to move through their gills. Some sharks achieve this by remaining in motion at all times. Moving sharks may not sleep at all. read more

So, when they sleep, they shut down part of their brain to rest, but keep enough of it active so they can continue swimming and, er, surviving. You just watch, humans will find a way to do this in the next 50 years and work loads will triple. read more

Shark species that need to swim constantly to keep water moving over their gills seem to have active periods and restful periods, rather than undergoing deep sleep like we do. They seem to be “sleep swimming,” with parts of their brain less active, or "resting," while the shark remains swimming. read more