The victim, believed to be in her 30s, sustained serious injuries to her arm and leg, according to police. She is in a critical condition.

A witness told Australian news outlet news.com.au that a lifeguard on a surfboard raced to assist the woman after screams were heard.

"I saw the shark's fins," the witness said.

"A swimmer was doing laps not far from shore. The lifeguard made an X symbol with his arms and the shark alarm sounded."

The witness also reported seeing "a lot of blood" in the water, adding that the swimmer appeared to have sustained a bite to the torso.

New South Wales police stated that the woman was pulled from the water by members of the public, who began administering first aid before emergency services arrived on the scene.

Officers then provided further first aid before the woman was airlifted to hospital by helicopter.

Nearby beaches, including Coogee, Clovelly and Bronte, have since been closed to the public.

Just months prior, a 12-year-old boy was attacked by a shark in Sydney.

Nico Antic was mauled in Sydney's east on Sunday, January 18 and tragically died later that month, in what proved to be the first in a series of shark attacks that followed in the days after he was hospitalised.