The family of 12-year-old Nico Antic has announced he has died after being attacked by a shark in Sydney Harbour.

Nico was the first victim in a recent spate of shark attacks in NSW, bitten after jumping off a 6m rock with two mates in Vaucluse about 4.20pm on Sunday.

One of his friends jumped into the water and dragged him onto the rocks.

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

His parents, Lorena and Juan, announced on Saturday that he tragically succumbed to his injuries.

“We are heartbroken to share that our son, Nico, has passed away,” they said in a statement.

“Nico was a happy, friendly, and sporty young boy with the most kind and generous spirit. He was always full of life and that’s how we’ll remember him.

“We would like to sincerely thank the first responders and the teams at Sydney Children’s Hospital, Randwick for everything they did to care for Nico.

“We would also like to thank everyone in the community for their support and kind messages.”

Juan, a surf lifesaver, changed his social media profile photo to an image of Nico on Wednesday morning, prompting an outpouring of prayers and tributes from friends.

The friend who pulled Nico from the water said he was proud of how long the boy fought.

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

“He was the most stubborn person I know and I’m grateful I was there for his last moments awake.

“There was a brief second where Nico woke up while he was bleeding and he just looked at me and then stopped and I thought I lost him, and I’m so surprised he fought for so long.”

A family friend told 7NEWS.com.au Nico was a “very sporty” kid who was “lovely, always happy, loved his relatives and was great at telling jokes”.

Other heartbroken friends have since paid tribute to Nico, who was due to turn 13 in February.

He is being remembered as a kind, fun-loving, sporty boy who shared memes that made his friends laugh.

“Fly high Nico, you were such a nice kid and a gun at rugby,” one friend wrote.

“It hurts to see you go this early. No one deserves to lose their life this young.

“You were such a nice kid and such a fun kid to hang around, and all the memes we’ve had throughout primary and year 7.

“Already miss you loads, fly high brother.”

Another friend said they were still struggling to accept his death.

“I don’t know what I’ll do without you,” they wrote.

“Every time I was with you, you made everything feel more fun, no matter what it was.

“Still can’t accept that you’re gone, it doesn’t feel real. I keep feeling like (you) will pop out and tell me it was just a prank and that you’ll be back like nothing happened.

“You were one of the strongest and kindest people I’ve ever known.

“I know you’re in a better place now, but it doesn’t make missing you any easier. Rest in peace, Nico. You will always be loved, and you will never be forgotten.”

More friends from the close-knit group said they were struggling to come to terms with the devastating news.

“Can’t believe you’re gone it doesn’t feel real at all and I keep thinking ur gonna message or show up or ask to hang,” one wrote.

“I miss you so much and everything reminds me of you, the beach, the jokes, just hanging out.”

A GoFundMe page has 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 have now been closed following the attacks.

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.