Few sharks are going to have a Jaws-like hissy fit near
divers. Still, manufacturers are coming up with products
to keep them at bay.
Shark Shield, introduced three years ago, is now
  available in a second version called Freedom7, onethird
  the size of the original and attaching to the ankle
  instead of the tank. It generates an electrical field, or a
  “shark-safe zone,” 26 feet in diameter around the diver.
  Electrodes generate a pulsing sensation detected by the
  shark through its sensory receptors, and create muscular
  spasms that cause the shark to immediately flee.
  However, say Shark Shield’s Australian makers, there is
  no lasting effect to the shark once it’s left. And the transmitter
  only repels transmitter sharks. The Shark Field
  Freedom7 retails for $596 and comes with a charger and seven-hour battery. More details about Freedom7 are at
www.sharkshield.com.
How about shark repellant you can just slather on
  your skin? A team of marine scientists at the University
  of Miami believes it has created just that, the first sharkrepelling
  sunblock. The lotion, now in its final testing
  stage, operates on pheromones and “just one application
  will protect swimmers in the surf,” says lead researcher
  Patrick Rice. But divers won’t be quite as protected – the
  sunblock/shark repellent only works for 30 minutes
  before it needs to be reapplied. Teeka Tan, the company
  that will market it, says it’s still working on liability
  issues around the sunblock (in case someone wearing it
  still gets bitten) but plans to have it on shelves in 2008.