Sharks produce – and pick up – tiny electric fields, to hunt their prey. Navy researchers are looking to pull off the same trick, so they can spot underwater mines.

Inside sharks' heads are jelly-filled canals called "the ampullae of Lorenzini," which the predators use to detect the itty-bitty electrical charges a fish makes when it flexes its muscles, or swims counter to the earth's natural magnetic fields. It's a real-live sixth sense. And it's way more accurate the sharks' eyesight.

The Navy is hoping the kind of sensors work better than sonar, too. Acoustic mine detectors have a hard time operating in the crowded, shallow waters near the coasts. There's too much happening there to get a clear signal. But with an electrical charge, there's a chance to could be noticed, instead. So the Navy is asking for proposals on how to build a set of Lorenzini's ampullae for people.

The device should be small – less than three feet long, the Navy counsels. And it should be able to pick up electrical signals of small, moving objects in fresh, brackish, or salt water.

At first, the Navy is looking for a few companies just to develop ideas for the detectors. Then, a few prototypes. But if all that goes well, the Navy promises, the system "will have immediate use in surveillance and monitoring operations with Homeland Security, Global War on Terrorism, Joint Forces Operations, and future combat systems under development." Happy hunting.

(photo credit: Callaghan Fritz-Cope/Pelagic Shark Research Foundation)