The Science of Shark Attacks

On the other side of the world on the west coast of Australia, a group of swimmers confrontation with a Great White revealed how selective a shark can be when choosing its prey. In Perth there is a local swimming group called the Pod. One of their members was businessman Ken Crew. The morning of November 6th 2000 started like any other. The 'pod' met on the beach for their usual 6.30am swim. At the end of the swim over a dozen of the members stood chest deep water. Then suddenly someone yelled 'Shark! Get out of the water!' The swimmers fled for their lives. The Great White caught Ken in its massive jaws. The shark had bitten off his right leg, slicing through a major artery. He'd bled to death in seconds. But how and why did the shark single out Ken Crew, in the middle of such a large group of swimmers?

Something about the movement and position of Ken Crew made him more vulnerable then the other swimmers. The Great White has better colour vision than any other shark - it's this hunter's greatest asset. It may have watched him from several hundred yards offshore. It can stalk its prey with one eye above the water's surface, picking the moment to close in and strike. As it approaches, a Great White rolls its eyes back into their sockets. Now attacking blind the Great White switches to electro detection. The human body is full of electrolytes and our breathing creates electrical fields that the shark can home in on. Sensitive capillaries on the snout can detect currents as low as one 5 billionth of a volt. In the attack on Ken Crew, the electrical activity from his beating heart may have been enough for the shark to home in on.

But Australia and South Africa are not the only place with a treacherous coastline. Around the world there are 14 shark attack hot spots. Danger zones where people are at greatest risk. As our fascination with using the sea for leisure increases, so do the number of attacks. 98 of them have happened in the warm tropical waters of Hawaii.

Three years ago housewife Laurie Boyette decided to take the long trip from Rhode Island to Kona, Hawaii for a family vacation. She went swimming in the sea with her nephew; both were strong swimmers.

"I actually had a premonition that if there was a shark this is where it would be and at that point I was a little bit past a raft which was maybe a 150 yards out. And I thought that was a very strange thought to have but it didn't scare me I just wondered where it came from."