By Steve Kingstone
BBC News, Brazil
With seemingly endless sunshine and a gentle breeze coming off the sea,
Praia de Boa Viagem in the city of Recife looks like the perfect urban beach.
And it is - but for one detail. Sharks.
Before the 1990s, there were virtually no attacks reported here. But since 1992, there have been 47 shark attacks along a 20-km (12.5-mile) stretch of coast. Sixteen of them were fatal.
In 2004, there were seven reported attacks. Two of the victims died.
"I was surfing 15m from the beach when the shark appeared under me," recalls 25-year-old Mario Cesar.
"I tried to punch him, but he took my arm and pulled me into the water. Eventually, I wrenched myself free and a big wave pushed me in to shore."
Mario lost his right arm in the attack, which happened in 2002. Another survivor is 18-year-old Walmir da Silva, who was attacked while swimming in water barely up to his waist.
Today, he wears a prosthetic leg below the left knee, and is waiting for a prosthetic arm to be fitted.
"The shark pulled me under with so much power that I really thought I was going to die," says Walmir. "And I was losing blood from my leg. But I hit his dorsal fin and kicked out - and in the end he released me."
In absolute terms, there are more shark attacks in Florida and Australia than in Brazil.
But statistically, a higher proportion of attack victims have died in Recife. One in every three attacks is fatal.
The perpetrators are mostly bull sharks, an aggressive species with a preference for shallow coastal waters.
The new port handles four million tonnes of cargo a year
So why are the attacks happening?
A state-funded investigation has focused on the long-term ecological effects
of a new port, to the south of Recife.
Porto Suape opened for business in 1984, and today handles more than four million tonnes of cargo per year. To facilitate its initial construction, two freshwater estuaries - which had discharged into the Atlantic Ocean - were sealed off.
"Female bull sharks used to enter those estuaries to give birth," says Fabio Hazin, a marine biologist and head of the state-funded monitoring comittee.
"From when the port was built, we believe a number of females moved north to the next estuary - which discharges on to the stretch of beach where the attacks happened."
Based on that finding, local human rights lawyers are considering a symbolic legal challenge to the state of Pernambuco, with the aim of securing compensation for the victims of attacks.
"Until now, not one victim has received compensation," says Sergio Murilo, a lawyer and the head of the Safe Beach Project - a local campaign group.
The government is under pressure to act over the attacks
"These people have lost limbs because of attacks, and they're getting no assistance.
"They need medical care and help getting a job. Compensation is about guaranteeing their right to a normal life."
The Safe Beach Project has also proposed a solution to Recife's shark problem.
It wants the local authorities to partition off a short section of beach using heavy-duty nets out to sea. Electromagnetic buoys would also deter - but not kill - the sharks.
Similar schemes have been tried in South Africa and Australia, but the idea has met with opposition in Recife.
"The problem with nets is that they wouldn't only stop sharks," says marine biologist Fabio Hazin. "Other creatures like dolphins and turtles would also get tangled up."
At the water's edge, Mario Cesar says that he would like to surf again one day - in spite of having suffered a terrifying attack.
"I'd need a better prosthetic arm," he says, "maybe a mechanical one which allows hand movement. And of course, I would have to be somewhere that, categorically, does not have sharks."