We binge watched shark shows on National Geographic Channel over the weekend, since it rained here all weekend.
Saw this one show where they put a MAGNET about the size of a brick and an actual brick in the tank with a small shark. The shark avoided the magnet.
This could possibly make a good shark repellant scheme, a few poles in the water with magnets, or even swimwear with magnets!................
You'd be digested by the time a shark might even notice magnets small enough for swimwear. Might give him a bit of revenge-indigestion though..;)