There is no parental care. Their diet includes nearly every animal in the sea, including their own kind. Although their voracity is legendary, they also fast for long periods, when they subsist on the oil in their livers. Large numbers of sharks attracted to the same bait become a whirling, vicious circle of activity with jaws snapping, tearing, and ripping not only into the food source but also into each other. Sharks' fins are relatively stationary, and the pectoral fins are not retractile as are the pectorals of some bony fish.
Most sharks swim constantly but leisurely, propelled by the sculling motion of the body and tail.
They are capable of sudden bursts of speed, measured at over 40 mph in the blue shark. Frequently, sharks are accompanied by pilot fish and remoras, two bony fish that commonly escort larger animals or objects. The pilot fish does not lead the shark to prey, as was once believed, and it escapes the shark's jaws only because of its own agility and not the shark's acceptance of the pilot fish. Remoras have been found in the stomachs of sharks, so this is not always a beneficial arrangement for them. Perhaps the most distinctive feature of sharks and undoubtedly one of the most important reasons for their success is their well-developed sensory system.