I saw a documentary recently on how some magnetic fields repel sharks. They are testing fishing tackle that will reduce the number of sharks that are caught inadvertently.
http://www.wired.com/gadgets/miscell...5/sharkmagnets
SharkDefense won $25,000 from the World Wildlife Fund's annual International Smart Gear Competition to develop magnets or metals to keep sharks from dying on commercial fishing lines intended for other fish, such as swordfish -- which they do in great numbers daily.