Some windsurfers and surfers worry about sharks, some don't, and some lie about it. I myself don't worry about sharks, but I prefer to waterstart as fast as humanly possible when I fall in the ocean.
For those windsurfers who do worry about being eaten alive or losing a limb to these fish, shark repelling technology would be a welcome bit of gear to add to one's quiver. Unfortunately the stuff is still in beta. Or alpha. Engadget reports on a test of a new electronic shark repelling system from Australia called Shark Shield. They put the thing on a surfboard and sent it out into sharky waters off of South Africa. A Great White swam up and bit the device.
Maybe the batteries were in wrong.