What does salt water have to do with electricity? Salt water is an ionic solution, meaning it contains particles with unpaired electrons. Because of this quality, salt water can also act as an electrical conductor. When a charged magnet comes into contact with salt water, the ions flow through the metal to become stabilized, resulting in the electrical field. We know that sharks can sense shifts in the surrounding underwater electrical fields through their ampullae of Lorenzini. Running into these stronger electric fields caused by magnets may overwhelm the sense and send them swimming in the opposite direction.
Yet, therein lies the problem. Initial testing revealed that the magnetic field only deters sharks up to around a foot (0.3 meters) away [source: World Wildlife Fund]. If this is the case, people would need multiple magnets scattered across their bodies for adequate security [source: Rajewski]. Also, you have to arrange the magnets with their poles facing outward because opposite poles attract [source: Rajewski]. The distribution and weight of the additional metals could make it difficult to swim.
Because of these potential pitfalls, this new technology will probably make a greater impact on the commercial fishing industry rather than on swimmers and surfers. According to the World Conservation Union, 20 percent of sharks are on the brink of extinction [source: WWF]. Much of this problem stems from the millions of sharks commercial fisheries accidentally hook and net each year.
To alleviate this problem, the patent application also proposes using the electropositive metals on pelagic fishing hooks and long lines to divert sharks from the bait, reducing the number unintentionally caught [source: Stroud]. This idea earned SharkDefense the 2006 grand prize from the World Wildlife Fund's International Smart Gear Competition [source: WWF].
Now, the National Oceanic and Atmospheric Administration is conducting a more detailed study on the potential of this technology, together with SharkDefense and other researchers. During the summer of 2008, it will test the magnets' deterrent strength and consistency in open ocean waters. Ocean Magnetics, an offshoot company of SharkDefense, also is looking into the feasibility of magnetic fences that could be installed around swimming areas to keep sharks out.
What else have people tried to use to keep sharks away? Read about the history of shark repellents on the next page.