Question: Hi! Is it true that a shark never stops smimmimg?

Rupert Marshall answered on 10 Mar 2017:

Not quite. People often think that sharks need to keep moving to keep water passing over their gills so they can get oxygen. It’s like thinking humans need to keep walking to force air into their lungs – but we don’t because we can breathe in and out, using muscles to suck air in and push it out again, even when we’re watching tv on the sofa. Many sharks do something similar in water: they have a pump that pumps water over their gills even when they are still. This means they can still collect oxygen and “breathe” even when they are not swimming