New video footage captured by scuba divers in Revillagigedo, Mexico, shows the common—but rarely recorded—sleeping habits of sharks. In it, a pack of whitetip reef sharks can be seen piled on one another in a cuddly, sleep-like state.

It is important to note that "sleep" means something much different for sharks: Unlike human beings, sharks do not enter an unconscious state when they sleep—rather, they toggle between "wakeful" and "restful" states. Little is known about what transpires during this period of rest.

Apart from its rarity, this footage is significant in that it offers a clear case against a popular myth: that sharks need continuous movement to avoid drowning. While it is true that some species, like great whites, move during resting periods for oxygen, whitetip reef sharks can remain completely motionless while still receiving water through their spiracles. They often rest during the day and feed at night on small bony fishes, octopuses, and crabs.

Watch the full video from National Geographic below: