Australian authorities said Sunday they will not attempt to hunt down a shark believed to have killed a swimmer, as reports said the victim would not have wanted the predator to die.Police suspect that avid diver and fisherman Brian Guest, 51, was taken by a shark as he was snorkelling with his son near Rockingham, south of Perth on Australia's west coast, on Saturday.Witnesses saw flashes of fins and blood in the water and nothing has been found of Guest except some shreds believed to have come from his wetsuit.Fremantle Water Police, who were Sunday searching the area for any remains, said there would be no attempt to hunt the shark."There's no way of knowing which shark it would be," Senior Sergeant Greg Trew said. "We could hunt down every shark from here to eternity without knowing whether we had the right one."Reports said that Guest had a deep respect for the ocean and its hazards and would not have wanted the animal killed."I have always had an understanding with my wife that if a shark or ocean accident caused my death then so be it," he wrote on a fishing website forum in 2004, national news agency AAP said.The sentiment was echoed by an unnamed family friend who was quoted as telling Western Australia's Sunday Times that Guest was aware that those using the ocean were "in their (sharks') territory"."He was a man of the sea. We are just glad he went on the ocean. It was his passion," the friend said.Leading shark researcher Rory McAuley said despite the idea perpetuated by Hollywood movies such as "Jaws" that sharks would repeatedly attack, this view was not held up by science."The old theory of the rogue shark that gets a taste for humans and repeatedly attacks has really been discredited over the past 30 years," said McAuley, a senior research scientist with the state Department of Fisheries."What we are talking about here is probably a white pointer shark and white pointers are very mobile, highly migratory, so the ones in Perth are transient and don't hang around long," he told The Sunday Times."There is no one reason why sharks attack."As the search for Guest continued, another man was recounting his close shave with a five-metre (16 foot) great white shark in a separate incident off a northern Sydney beach on Saturday.Steve Kulcsar's kayak was hit by the shark, knocking him into the sea and forcing him to tread water for a minute as the giant fish swam rings around him on, reports said."A fisherman yelled out, 'There's a five-metre shark coming your way.' We all thought he was just trying to stir us up for a laugh, but a few moments later a big fin appeared," Kulcsar told the Sunday Telegraph newspaper.Seconds later, Kulcsar was knocked into the water as the shark bumped the kayak and it took him a minute to struggle back into his boat from which the fisherman pulled him into theirs.Sharks are a common feature of Australian waters. Even the maxi yacht Wild Oats XI collided briefly with a large shark on Tasmania's east coast before going on to win the Sydney to Hobart ocean race on Sunday. Some 194 people have died in shark attacks in Australia over the past two centuries. In the most recent, a 16-year-old was killed while surfing in the northeast earlier this year, according to the Australian Shark Attack File.