Sharks have a keen sense of hearing and can smell blood for from a 2000 yards away. sharks also have a special system of channels in their skin that them feel the vibrations of a splashing swimmer. we know that in clearwater, sharks can see dinner from about 50 feet away. if you ever spot a shark, always swim away smoothly! what is the main idea? a. how well sharks hear. b. why sharks have poor vision. c. how sharks sense food. d. when to swim away smoothly.