Is this a different model to the one used by spearfishermen and scuba divers? Does movement render them useless also?

http://www.theaustralian.news.com.au/story/0,25197,23300091-32682,00.html

AN electronic device designed to ward sharks away from surfers failed so spectacularly during a trial off South Africa that it was eaten by a great white.

An inquest heard yesterday the Shark Shield surf model was activated on a float carrying bait when the 3.6m female shark approached. Rather than being deterred by the device, the shark, under the gaze of the Natal Sharks Board, bit into it.

South Australian Deputy State Coroner Tony Schapel yesterday heard of the test failure during the inquest into the death of Jarrod Stehbens, who was taken by a great white shark while diving off Glenelg in South Australia in 2005.

Mr Hartley said the failed South African test on the surf unit - which has been held back from release into the marketplace - was due to a problem with the electrode's configuration. The device was now packaged with a large disclaimer warning it would only repel sharks when the surfer was still in the water waiting for a wave.

"The surf product only can be guaranteed to work when it's stationary, not when it's surfing in the wave or paddling," Mr Hartley said.