A 12-year-old boy is in for the “fight of his life” after being attacked by a large shark while swimming in Sydney Harbour on Sunday afternoon.

New South Wales police said the boy was jumping off a popular rock ledge near Nielsen park in Sydney’s east about 4.20pm on Sunday with friends when the attack, possibly by a bull shark, took place.

The boy’s friends, all of similar ages, rushed to assist him, with at least one jumping into the water to pull him to safety.

Supt Joe McNulty, the commander of NSW police’s marine area command, praised the friends for their quick response.

“The actions of his mates who’ve gone into the water and pulled him out have been nothing but brave,” McNulty said, adding praise to emergency responders.

“All I can say is the actions between police … the team who were doing CPR at the time, it was extraordinary. It was a textbook recovery to give this boy a fighting chance for survival. He’s in for the fight of his life now, and the actions of emergency services yesterday gave him that chance.”

_{Sign up: AU Breaking News email}

A nearby police speedboat responded within minutes, where an officer applied a double tourniquet to both of the boy’s legs to stop the bleeding. Officers were administering CPR as the boy was taken by boat to nearby Rose Bay, where ambulance crews were waiting to rush him to hospital.

He remained in critical condition with injuries to both legs.

The Department of Primary Industries had not yet confirmed what species of shark was thought to be involved, but police officials said it was a “large” animal.

McNulty noted Sydney Harbour was brackish, meaning it contained a mixture of salt and freshwater, which can worsen visibility.

After a weekend of heavy rain, he said officials believed the water quality, as well as the splashing from people jumping into the water off the rocks, “may have made that perfect storm environment for the shark attack”.

“At the moment we’ve experienced a lot of fresh water in the harbour, it’s brackish water, so you can’t see the bottom,” he said. “So I would recommend not swimming there right now. It’s not a good time to swim.”

NSW SharkSmart confirmed that beaches in the vicinity of Nielsen Park, including Shark Bay beach and Camp Cove beach, remained closed after the incident.

Insp Giles Buchanan with NSW ambulance said the tourniquet applied by officers shortly after the attack was “definitely a life-saving intervention”. He described the initial response to the attack as a “resuscitation situation”, noting the boy was unconscious when emergency officials first arrived.

The boy had to be intubated to assist with breathing.

“I think it was touch-and-go the entire time,” Buchanan added. “It still is.”

Shark attacks are rare in Sydney Harbour, but they do happen. In 2024, a woman was seriously injured after a bull shark bit her leg in Elizabeth Bay as she was taking a “short dip” off a pier close to shore.