Hold your hands out about three feet
apart. That's about the distance at which
some large sharks can sense electric fields given off by prey. Move your hands
so that they are about six inches apart. Smaller sharks detect electric
fields at that distance.
All living things (even you) produce an electric field, given off by each
heartbeat and muscle movement. A shark has special receptors located around the
head that detect electric fields. These receptors can help a shark find a fish
hidden under the sand by detecting its heartbeat. A shark also uses this sense
to position its head and mouth when moving in for the final attack. This is the
only sense a shark has that you don't share.