Last summer, up and down the relatively short area of the Outer Banks of North Carolina , we had 11 shark attacks. We're in the water everyday so I ordered some "Noshark" devices from www.bluvand.com. They are designed to start making the shark uncomfortable at roughly 7 meters, and the discomfort is supposed to become unbearable for the shark at about 3.5 meters. All I know is that we wore them in those waters daily and are still in one piece. Check out their web site and videos.
bluvand.com/