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Still Waters

Magnets have been found to scare off sharks

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Divers often resort to metal armour, harpoons or simply staying in a cage to protect themselves from sharks, but researchers have shown that magnets could be the way to ensure ‘elf and safety beneath the waves.

Chemist Eric Stroud runs a U.S research company called SharkDefense, and he’s proved that some sharks cannot bear to be near magnets.

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I think I would feel more safe in a shark cage, spear gun and octupus ink.

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It makes sense. I remember reading about the electromagnetic sensors in sharks and how specialised some of them are. Hammer heads spring to mind, they can detect the electromagnetic field of a sleeping fish hidden under the gravel on the sea bed by sweeping their head back and forth like a metal detector. Makes sense that an animal with such specialised evolved senses would be vulnerable to interference in the same way that we can't hear past very loud noise or see if 'blinded' by bright light.

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Maybe they should fit strong magnets into surfboards, or would this make them too heavy? Just a thought :)

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I used to work in the marine sciences in a VERY shark prone area (Port Lincoln - great whites + tuna farms), and we had a set of Shark Pods - these were rechargable battery-driven electromagnetic-field generating devices. They have been in use since the 1990's - so the basic principle isn't all that new.

We were involved in some of the testing, and when the results were all put together it showed a number of important things, inc:

- different shark breeds showed vastly different responses, and some seemed to be completely unaffected

- they had extremely limited usefulness, in terms of range (only a few metres, if that)

- they had little or no effect whatsoever on sharks who were aggressively feeding - and that doesn't mean a 'frenzy', it includes them just being very hungry, so a shark making a 'run' at you from say 4 metres, will very likely just keep coming and complete the attack..

In short, it was very hit and miss. There have been reports of divers being attacked while wearing them (thankfully not those under my watch!), sadly including the death of one of later developers of the technology (although it is disputed whether he was wearing one at the time).

{{Note that the pods I'm familiar with used an alternating e-m field, not just a static magnet, but the developers had supposedly tried all types of fields and settled on the frequency used as the most generally effective. Note also that Lemon sharks are not found hereabouts (Australia) to my knowledge - and I don't think they are regarded as a dangerous man-eater anyway..}}

Because the pods were time-consuming to fit and test, had a fairly limited run-time, and added to the bulk and awkwardness of scuba gear, most of our divers (myself included) just didn't bother with them after initially giving them a go.

If they were smaller (which they are now, I believe) and much more widely effective, maybe they would be more worthwhile.

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