Sharks evolved over 400 million years ago, before the first dinosaurs. Clearly they are well adapted to their environment. Indeed, they have changed very little in that time. Let's follow a shark as it hunts and attacks its prey. In their murky open-ocean environment, vision is important at a range of about fifteen meters or less, but it is not the primary sense for spotting potential prey at great distances.
Sound travels almost five times faster in water than on land, and sharks have keen sense of hearing.
Sharks are particularly sensitive to low frequency sounds, such as those made by wounded, thrashing animals. On each side of the shark's body runs a row of small holes connecting an internal canal called the lateral line which is sensitive to nearby movements. In their snout area sharks have pits, known as ampullae of Lorenzini, which detect the small electrical signals that all animals, including human beings, emit. This sense works best at close range and enables the shark to pinpoint an animal it may not even see in dark water. Metal objects also emit electrical pulses, a fact that may help explain why sharks sometimes attack boats, docks and steel cages.