Four attacks in 48 hours: How east Australia's beaches became a 'perfect storm' for sharks
It's "extraordinary", says shark researcher Chris Pepin-Neff: four shark bites within 48 hours, and three of them within a 15-kilometre stretch of Australia's east coast.
On 18 January, a 12-year-old boy was taken to hospital with critical injuries and later died after being attacked while swimming in Sydney Harbour. The next day, an 11-year-old's surfboard was bitten at Dee Why beach, hours before a man was attacked at nearby Manly and taken to hospital in critical condition.
Then, on 20 January, a fourth surfer "sustained a wound to his chest" after a shark bit his board some 300km (186 miles) up the coast.
"This is the closest - in both proximity and in time - series of shark bites that I've ever seen in my 20 years of research," says Pepin-Neff, who is an associate professor of public policy at the University of Sydney.
The rapid spate of incidents triggered local and international alarm, with dozens of beaches closed amid fear of further attacks. Predictably, calls for shark culls have gathered momentum and volume.
Experts, however, have cautioned against such measures, advocating instead for a greater awareness of shark behaviour and urging a rethink of humans' relationship to these fish.
There are multiple factors that likely contributed to the recent spate of incidents, they say – and it's not the sharks that are the problem.
Why suddenly so many shark attacks in Australia?
Non-provoked shark attacks are usually precipitated by environmental conditions, attractants in the water, or both.
The three recent incidents in Sydney - all of which are thought to have involved bull sharks – followed several days' worth of heavy rain, during which the city's official weather station recorded 127 millimetres of downpour within 24 hours – its wettest January day in 38 years.
That rainfall would have created "perfect conditions" for bull sharks, according to Rebecca Olive, senior research fellow at RMIT University.
"Bull sharks thrive in warm, brackish water, which most other sharks flee," she told the BBC. "They love river mouths and estuaries, so the freshwater that flooded off the land following the recent rain events was perfect for them."
Olive and other experts further note that this freshwater would have likely flushed sewage and nutrients into the sea, thus drawing in bait fish and, in turn, sharks.
"There's clearly an attractant in the water," Pepin-Neff says, suggesting that a "perfect storm" of low salinity freshwater could have created a "biodiversity explosion".
"The bait fish come to the surface, the bull sharks come to the surface, everybody's in the near shore area – and now we have a problem."
Are shark attacks increasing overall?
Official statistics show that shark bite incidents in Australia have gradually increased over the past 30 years – rising from around eight to 10 per year in the 1990s, to yearly averages in the mid-20s from the 2010s onwards.
That doesn't mean sharks are becoming more aggressive, though. More likely is that the higher numbers reflect better data collection, as well as a number of compounding human factors.
These include a growing coastal population, an increased uptake of water sports and thicker wetsuits that allow swimmers to stay in the ocean for longer.
"The number of total encounters is definitely much higher than it was, just because the population of people who go in the water and do all these things is really high," Pepin-Neff explains.
They also point out, however, that the rate of shark bites "doesn't tick up at the amount it should for the proportion of people who are going in the water and doing more things".