A shark also uses this sense to position its head and mouth when moving in for final attack. Scientists estimate the number of living shark species at more than 350. More than 42 species of sharks live off the North Carolina coast of which 28 are common. Sharks are unable to distinguish between natural signals and those produced by artificial objects such as metal and wire. This may explain why sharks sometimes attack boats, docks, and steel cages.
Sharks have one of the keenest senses of smell of any animal.
They can scent from great distances and their sensitivity to smell seems to increase the longer they have been without food. Sharks also have well-developed inner ears that enable them to hear sounds more than a half mile away. They are particularly sensitive to irregular, low-frequency sounds, precisely the kinds of sounds made by fish that are injured and swimming erratically. A shark's sense of touch is stimulated by direct contact or water movement. A special system called a lateral line, a narrow strip of sensory cells that runs along the sides of the body, allows them to detect changes in water pressure and pick up vibrations in the water.