“Sharks need to keep swimming to breathe.”

The notion that all sharks must perpetually swim to breathe is a widespread misunderstanding, often reinforced by dramatic portrayals of active marine predators. This belief stems from the reality that some shark species, known as obligate ram ventilators, indeed rely on constant forward motion to force oxygen-rich water over their gills. Without this continuous flow, sharks such as great whites, mako sharks, and whale sharks would suffocate, as their respiratory system is designed to extract oxygen solely through movement.

However, this necessity applies to only a minority of the over 500 known shark species. Many other sharks employ a different method called buccal pumping, which allows them to actively draw water into their mouths and pump it over their gills even while stationary. Species like nurse sharks, bullhead sharks, and wobbegongs are adept at this, enabling them to rest on the seafloor or hide in crevices without risk of asphyxiation. Some even possess specialized openings behind their eyes, called spiracles, to assist in this process, particularly when their mouths are obscured.

The misconception likely gained traction because early scientific understanding, observing the lack of opercula (gill covers) in sharks that bony fish use to pump water, led to the assumption that all sharks needed to swim to respire. Furthermore, popular media frequently highlights the large, fast-swimming obligate ram ventilators, making their unique breathing strategy seem universal. While sharks also lack a swim bladder and rely on movement and an oily liver for buoyancy, which can contribute to the belief in constant motion, this is distinct from their respiratory needs.