If sharks can't stop because they'll drown, how do they sleep?

Sharks that can stop swimming in order to rest use specialized apparatus known as spiracles to force oxygen-rich water through their gill system. ... If they are restrained in something like a fishing net (which happens all too frequently!), they experience hypoxia, or lack of oxygen, and drown. read more

The idea that sharks will drown if they stop swimming is a common one, but it's not entirely true. There are two main ways sharks go about breathing. Ancient shark species breathed through a method called buccal pumping, which some of today's sharks still use. read more

Florida Program for Shark Research Director George H. Burgess discussed the lack of knowledge around shark sleep with the Van Winkle's blog and says some sharks may rest during "yo-yo swimming," when they actively swim to the surface but rest as they descend. read more

They swim by waving their body in side-to-side curves. It starts with the head turning first one way, then another. The movement ripples down their torpedo-shaped body, pushing the water away and providing forward propulsion. read more