Do all sharks need to keep moving to stay alive?

Yesterday, one of my P6 pupils shared with the class that he had read in a National Geographic Magazine that sharks need to keep moving to stay alive.

Do all sharks need to keep moving to stay alive? It depends on the breathing technique the sharks use. Ancient shark species do not have to constantly swim to breathe as they pump water through their mouth and over their gills. This method is known as buccal pumping. The sharks use their buccal, or cheek, muscles to pull the water into the mouth and over the gills. Examples of shark species that use this method of breathing are nurse sharks, angel sharks and carpet sharks. Most of these species have a more prominent spiracle, which is a tube behind the eyes. When a shark is at the bottom of the ocean floor and cannot breathe through its mouth, the spiracle acts like a mouth by pulling in water.

Over time, sharks evolved and the modern shark species use a method known as ram ventilation. By swimming fast, these sharks actively force water into their mouths for processing. Shark species that breathe using ram ventilation do use buccal pumping to breathe when they are idling.

There is a category of sharks known as obligate ram ventilators that are said to have to swim constantly to stay alive. Only about two dozen of the 400 identified shark species fall in this category. One such species is the great white shark.