One of the friends who pulled young shark attack victim Nico Antic out of the water has spoken about jumping in to try and save him.

Nico, 12, was jumping off a six-metre high rock with two mates in Sydney Harbour about 4.20pm on Sunday when he was attacked by what’s believed to have been a bull shark.

One of Nico’s friends has since been hailed a hero for immediately jumping into the water and dragging Nico onto the rocks while the shark lurked nearby.

Other friends then helped to pull him from the harbour before Water Police arrived and rendered first aid.

NSW Police Superintendent Joseph McNulty praised the bravery of Nico’s friends on Monday.

“The actions of his mates who have gone into the water to pull him out have been nothing but brave, a gallant recovery from his mates,” he said.

“Those young men are brave under those circumstances, and very confronting injuries for those boys to see. But I suppose that’s mateship.”

Nico was rushed to Sydney Children’s Hospital in Randwick with severe leg injuries and in a critical condition.

The friend who dragged him from the water said he was proud of Nico’s fight.

“He kept fighting and breathing in my arms and he never gave up for a second,” the friend said.

“He’s the most stubborn person I know.”

Emotional messages are being shared online about Nico, describing him as a kind, fun-loving, sporty boy who shared memes that made his friends laugh.

A GoFundMe page has also been set up to support Nico’s family during what has been described as an “incredibly difficult time”.

“Despite all efforts, this heartbreaking event has led to the worst possible outcome,” a close friend who started the fundraiser wrote.

“We are raising funds to help the Antic family cover upcoming expenses and related arrangements during this incredibly difficult time.

“Any contribution, no matter the size, would be deeply appreciated and will help ease the financial burden as they grieve. All funds will be donated to the Antic family.”

There have been four shark attacks along the NSW coastline since Sunday.

Just hours after Nico was attacked, an 11-year-old narrowly escaped injury when a shark took a large chunk out of his surfboard at Dee Why Point on Monday morning.

Later the same day, 27-year-old surfer, Andre de Ruyter, was dragged underwater during a shark attack at Manly Beach just after 6pm.

He was pulled unconscious from the water by fellow surfers and rushed to Royal North Shore Hospital in a critical condition.

Less than 24 hours later, 39-year-old surfer, Paul Zvirzdinas, was reportedly bitten by an “animal” while in the water at Point Plomer Beach, south of Crescent Head, on Tuesday.

He managed to drive himself to Kempsey District Hospital and has since been discharged.

All beaches in Sydney’s northern beaches region were closed following the attacks, but are expected to be open for the Australia Day long weekend.

More than 30 SMART (Shark-Management-Alert-In-RealTime) drumlines have been deployed along Sydney beaches, while shark listening stations and aerial surveillance have been ramped up.