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SYDNEY - The single-engine Cessna banks in a stomach-churning corkscrew over Bondi Beach.
"This is what we do when we see a shark," said the pilot, his voice crackling over the intercom system. "We orbit above and keep on top of it until everyone clears out of the water."
The Cessna is one of three distinctive red and yellow aircraft that maintain a vigil over the coastline of New South Wales, including Sydney and its busy ocean beaches.
The Australian Aerial Patrol's volunteer pilots and spotters insist that shark numbers are increasing as a result of official protection given to species such as the great white.
Last year the air crews spotted more than 200 sharks, including great whites, tigers, hammerheads and bronze whalers.
"Nobody can tell me sharks are diminishing in number," said Harry Mitchell, the Australian Aerial Patrols general manager.
"In the last five years we've seen a marked increase in shark numbers close to shore. I'd suggest that in particular there are more great whites out there than scientists estimate."
The debate over the threat posed by sharks in Australian waters has been given new urgency after a commercial diver's remarkable escape from the jaws of a great white last month.
Eric Nerhus, 41, feared he would be bitten in half when the 4m shark attacked him off Cape Howe, southern NSW, as he collected abalone from the ocean floor.
Nerhus was diving off a sparsely populated part of the coast where spotter aircraft do not venture.
Last Saturday a 26-year-old surfer was bitten by a shark while riding a wave off the NSW north coast. The man's foot was mauled in the attack off Shelly Beach, between Ballina and Lennox Head, police said. Lacerations to his lower left leg and foot were not life-threatening. The man told paramedics he was attacked from behind as he rode a wave on his boogie board.
Critics question how useful the patrols really are. The NSW government refuses to fund the service, arguing that it is hard to spot sharks from fast-moving aircraft.
The $600,000 it costs to keep the Australian Aerial Patrol flying each year instead comes from local council grants and corporate sponsors.
Scientists say that far from increasing, shark numbers are declining, partly because of chronic overfishing and Asian countries' demand for shark fin soup.
"I get sick and tired of people saying at the start of every summer that there are more sharks around than ever," said Dr John Paxton, a marine biologist at the Australian Museum in Sydney.
"It's rubbish. The firmest evidence we have is from the number of sharks caught in the nets which protect beaches, and those have gone down."
When nets were first strung across a handful of Sydney's beaches in 1937, 1500 sharks became entangled and died in the first 12 months.
Seventy years on, and with 49 beaches now protected by nets, fewer than 200 sharks are caught each year.
Environmentalists oppose the nets because they inadvertently catch and kill many other marine creatures, including turtles and dolphins.
Dr Paxton believes the concept behind aerial patrolling is equally flawed.
"What happens when the shark is in deep water and can't be seen by the aircraft? What happens if it's foraging among the kelp? The plane passes over, but the shark is still there."
But the Australian Aerial Patrol insists it saves people from shark attack.
When a crew spots a shark menacing surfers or swimmers, they radio lifesavers on the ground, who send out jetskis or inflatable boats to chase the predators out to sea.
"We see sharks just a few metres from people, sometimes in the first three rows of breaking waves," said Mr Mitchell. "If a shark is sick or old, it may not be able to go after its normal prey. It's then that its next target might be you or me."
