Man's love affair with the surf has always been tempered with the fear of the ultimate blue water predator, the shark. Until now that is... a new Australian invention makes it safe to go into the surf or sit "out the back" with your legs dangling in far greater safety. Adelaide-based SeaChange Technology has released the Shark Shield, a book-sized device that straps on to the thigh and repels sharks by emitting an electrical field via trailing antenna. A Sharks detects this electrical field through sensory receptors on its snout, initially causing mild irritation and as it swims closer, muscular spasms that drive the shark from the area. The Shark Shield is available in a general-purpose unit for surfing activities or as a kit designed specifically for divers which has the two electrodes at different points - one on the ankle and another on the scuba cylinder - creating a protective field all around the body.