The woman, aged in her 50s, was swimming about 20 metres offshore at Congwong Beach in Botany Bay National Park about 7pm when she was bitten.

The woman suffered deep lacerations and puncture marks to her left leg and foot, but managed to make her way towards the shore.

The woman, who was bleeding heavily from her wounds, was helped onto the sand by a number of nearby fishermen, who gave her first aid and called emergency services.

NSW Ambulance paramedics arrived at the beach a short time later and treated the woman for her injuries.

She was stretchered off the beach and taken to St George Hospital in a stable condition. The woman is expected to undergo surgery for her injuries on Saturday.

After assessing photographs of the woman's injuries, a shark biologist from the NSW Department of Primary Industries determined a great white shark was likely responsible for the bites.

Randwick Mayor Lindsay Shurey said the community was in shock following the attack.

“From all accounts the woman was very lucky and certainly the whole community's heartfelt thoughts are with her for a full recovery," she said.

“I’ve lived in the area for 25 years and this is the first confirmed shark attack in Randwick City. We’re all a little shocked and concerned.

“As a precaution, Council Lifeguards have immediately closed all the La Perouse beaches including including Congwong, Little Congwong, Yarra Bay and Frenchman’s Bay for at least Saturday."

She said lifeguards would also be stationed at beaches that are usually unpatrolled on Saturday to advise people not to swim.