How do sharks find their prey?

Contrary to popular belief, sharks do not use smell as their primary means to find food.  This is an important sense, but before this, sharks locate their food by sound and sound vibrations in the water.  They can actually hear a struggling fish from 2 km (3.2 miles) away.  Once they begin to close in on their prey their sense of smell helps them tremendously and they also have exceptional eyesight and can sense the electrical impulses produced by the muscle movements of their prey.  All of these senses together allow the shark to be a fierce predator.