Electrical Signals
All animals life gives off a weak electrical field. This allows fish to sense nearby objects without actually touching them. When a fish or seal is struggling,the movement of the fish sends a vibrating electrical signal through the water.Sharks can detect these electrical impulses underwater.These tiny signal are received by sensory organs in the shark's skin.These are called the Ampullae of Lorenzini.The ampullae are similar to pores in a person's skin. But they are larger and more sensitive.The hammerhead shark frequently uses this electroreception technique to hunt other fish in the ocean-often several kilometers away.