Swimmers in Sydney have been urged to stay out of the water after three people were seriously wounded during a spate of shark attacks in New South Wales.

Recent shark attacks may be linked less to shark behaviour – and more to the pollutants, pesticides and parasites humans send into the ocean.

The attacks have left two people in hospital, with people asking why bull sharks are having such an impact on New South Wales' beaches.

Sharks get a bad rap in most media. On the very rare occasions when a shark attacks a human, even when there are warnings that sharks are in the area, the sharks are at fault and anti-shark campaigns show up all over the place. Yes, sharks do attack humans ...

Bull sharks, explains Marcel Green, who leads the NSW Department of Primary Industries shark program, are opportunistic ambush predators. They do well in rivers and bays and at dusk and dawn when low visibility presents them with an advantage over their prey.

Although the number of shark attacks has declined in recent years, the long-term trend shows they have increased worldwide. Scientists say the main reason for this is tourism. Human population is increasing, so more people are visiting beaches and ...

Only a few hours earlier, a shark knocked an 11-year-old boy into the water at Dee Why—just north of Manly—and bit a chunk out of his surfboard. And on Sunday afternoon, a 12-year-old boy was bitten by what authorities believe was a bull shark while swimming at a popular beach in Sydney Harbor. He is still in a critical condition in hospital.

Three attacks in two days are the latest in a fourfold increase in shark bites along the NSW coast in recent years.