One of the victims of four shark attacks within the past 48 hours has been identified as 27-year-old Andre de Ruyter.

The South Coast musician remains in intensive care after he was mauled by what was believed to be a bull shark while swimming at North Steyne Beach in Manly about 6.20pm yesterday.

The former Austinmer Surf Life Saving Club volunteer has undergone surgery to have his lower right leg amputated following the attack.

The 27-year-old was attacked by a shark yesterday at a beach in Manly. (Supplied)
Andre de Ruyter remains in hospital following the attack. (Supplied)

A group pulled the 27-year-old from the water and began first aid as they waited for emergency services to arrive.

Multiple services, including paramedics, intensive care ambulance, a helicopter and police, responded to the incident.

He was taken to Royal North Shore Hospital in a critical condition.

The South Coast musician is one of four shark attack victims in NSW in the past 48 hours. (Supplied)

The NSW Department of Primary Industries say bull sharks are known to frequent Sydney Harbour, especially during the year’s warmer months, and can be found in shallow waterways.

Swimmers are advised to be careful, avoid the beaches, and stay clear of low-visibility and murky water.

Beaches between Town Breach and Crescent Head have been closed in the wake of the four separate incidents.