Simply Science 6
Sharks are indeed capable of staying still in the water, but their ability to do so can vary depending on the species and the circumstances. Some sharks are more capable of remaining stationary than others, and their ability to do so is often related to their hunting and feeding behaviour.
Many sharks have a method of gaining oxygen known as "ram ventilation." They must swim continuously to force water over their gills and extract oxygen from it. If they were to stop swimming, they could suffocate because they wouldn't receive enough oxygen. This is true for many active, pelagic (open ocean) species like the great white shark.
In contrast, some species of sharks are adapted to a more, shall we say, sedentary lifestyle. Bottom-dwelling sharks like the nurse shark or angel shark don’t rely on ram ventilation. These sharks can rest on the ocean floor (Benthic Species) and pump water over their gills without having to move continuously.
There are some species of sharks that can hover or stay relatively stationary in the water, using their pectoral fins to create lift and maintain their position. This is often observed in species like the hammerhead shark, which can hover motionless near the ocean floor.
Some sharks, such as grey reef sharks, also use currents to their advantage when they want to rest. By positioning themselves in areas with strong currents, they can maintain water flow over their gills and don’t have to actively swim – a great opportunity to have a nap!
Strangely, some sharks, like the mako shark, engage in "yo-yo swimming." They swim up to the warmer surface waters to raise their body temperature and then slowly descend to cooler depths to rest. During the descent, they may remain relatively still.
So, the idea that sharks can't stay still is not entirely accurate. While many species of shark need to keep swimming to maintain oxygen flow over their gills, there are exceptions, and some sharks have adaptations that allow them to rest or hover in the water.
Quite an amazing fish …