Sharks, one of nature's most fearsome killers, are coming in increasing numbers to feed in Sydney Harbour, where every weekend hundreds of sailing boats dot the water and thousands of bathers frolic in the coves.
Or are they?
Battle lines have been drawn between newspapers and some scientists who claim the cleanest Sydney Harbour waters in many years have boosted fish populations and the predators that feed off them, and sceptics who deride it all as "shark-ploitation."
The catch in mid-January of a three-metre (10 foot) Bull shark way up the Parramatta River which snakes from the harbour through Sydney suburbia was seen by some experts as unusual.
The Parramatta catch, headlined "Monster in our Midst" by the tabloid Daily Telegraph, made many locals wonder if a decades-long truce was ending between Sydneysiders and sharks. The last fatal shark attack in the harbour was in 1963.
Some professional divers, who spend most of their days swimming in the supposedly shark-infested waters of Sydney harbour and the surrounding coastline, think the local media is getting caught up in a shark headline frenzy after a number of attacks and sightings around the country.
"They're not after humans anyway. For the most part, if they take a bite out of you they'll realise you're not a fish and spit it out," said a 76-year-old veteran in a Sydney dive shop.
CLEANER WATER, MORE SHARKS
The New South Wales Environmental Protection Agency (EPA) said this week that the water off Sydney's ocean beaches was now cleaner than it had been in decades because of deep sea sewage outflows, stormwater drain improvements and public education.
It said that the same applied, to a slightly lesser extent, to the harbour itself and anecdotal evidence of an increase in fish and marine life was "incontrovertible."
"It's only anecdotal but it seems consistent. No one can doubt the harbour water is getting better and that's having a beneficial impact on wildlife, more fish, more sharks," said John Dengate of the EPA.
Australia has always had its sharks. Much maligned, they strike fear in most hearts but have actually killed far fewer people since European settlement than, for example, bee stings.
Nevertheless, the government is using their menacing presence off Australia's shores to try and deter illegal immigrants.
Frequent shark sightings that followed two fatal attacks last September by suspected Great Whites off South Australia, and two highly publicised attacks in Western Australia, have persuaded South Australia authorities to reinstitute aerial patrols.
Last Sunday, Mark Ellington of a cancer fundraising campaign called Kayaking for Kemo Kids said he was flung into the sea when what might have been a Mako shark rammed his kayak as he paddled down to Sydney from Queensland.
As for Sydney harbour, Dave Crass of Manly Oceanworld said on Wednesday that shark numbers were miniscule in comparison with 150 years ago, when hundreds would have been swimming in the water. But the sharks out there would certainly head for the food.
"If there are more food stocks in the water, then there will be more accommodation for large predators," Crass said.
The expert of Australian shark experts, John Stevens of the government-funded Commonwealth Scientific and Industrial Research Organisation's marine research division in Hobart, said the catch of the large Bull shark deep in the harbour was "fairly unusual."
SHARKS ALWAYS OUT THERE
But to say cleaner water meant more fish and therefore more sharks was a hypothesis that might not stand up to scrutiny.
"The thing is, sharks are always there. I'd think you'd be in for quite a surprise if they drained the harbour and you found out exactly how many are swimming about in there," he said.
Marine biologists question the thesis that clean water is simply good for ocean critters.
Strip out the "charismatic stuff" like seals, birds and big fish and you find that many lifeforms in the sea thrive in a crisis - such as contamination - as they madly reproduce to stabilise their numbers, said Tony Underwood, a professor and invertebrate biologist at Sydney University.
"Mostly, water quality has bugger all to do with anything," Underwood said. "With the sharks in Sydney you have to ask: Is it because now we can see them? They're no longer hidden by sewage?"