A man in his 20s has been critically injured after being bitten in the third shark attack in Sydney in two days.
A 12-year-old boy and an 11-year-old boy were also ambushed by a shark in the past few days.
The young surfer was bitten on his leg off North Steyne Beach in the northern suburb of Manly at 6.20pm local time on Monday.
Beach goers helped wrench him from the water and an ambulance took him to a hospital in a critical condition.
All of the Northern Beaches have been closed “until further notice”, police said.
It comes after a young boy was reported to have lost both his legs in a horrific attack just the previous day.
On Sunday, a 12-year-old boy suffered serious injuries to both legs after jumping from a 20ft high ledge known as Jump Rock near Shark Beach in Sydney Harbour in the eastern suburb of Vaucluse.
Police have said the boy's three friends saved his life by jumping from the cliff during the attack and dragging him back to shore.
"The actions of his mates who have gone into the water to pull him out have been nothing but brave," Superintendent Joseph McNulty told reporters.
"Those actions of those young men are brave under the circumstances and very confronting injuries for those boys to see," he added.
Some news reports said the boy lost both legs in the attack.
Around 12pm on Monday, an 11-year-old boy was on a surfboard that was attacked multiple times by a shark at Dee Why Beach, a few kilometres north of Manly. The shark bit off a 15cm chunk of the board, but the boy managed to escape uninjured.
Due to the size of the bite mark, it has been suggested the 11-year-old was attacked by a bull shark, a stout, powerful shark that can reach up to 11.5 feet long.
All three beaches near where the attacks occurred have some form of shark protection netting. It was not totally clear where the attacks occurred in relation to the netting.
Police had warned after the first attack that recent heavy rain over Sydney had increased the amount of fresh and murky water in the harbour, heightening the bull shark danger.
Dee Why Beach is close to Ocean Reef Beach, where a 57-year-old surfer was killed by a suspected white shark in September.
In November, a 25-year-old Swiss tourist was killed and her partner was seriously injured trying to save her as they swam off a national park north of Sydney.
