Why do sharks need to keep swimming?

Most sharks need to keep swimming to ensure water flows over their gills, enabling them to extract oxygen and breathe. This process is called “ram ventilation.” Some species, like nurse sharks, can pump water over their gills while stationary, allowing them to rest on the ocean floor. However, active swimmers like great white sharks rely on constant movement for respiration. Swimming also helps sharks maintain buoyancy and control their depth, as they lack a swim bladder.