The victim has been named as 35-year-old British man Simon Nellist, from Wolli Creek, a keen diver and a regular swimmer.

The ocean lover died from catastrophic injuries after being attacked by what witnesses say was a four-and-a-half metre great white shark at Buchan Point, between Little Bay Beach and Malabar Beach, on Wednesday.

It was the first fatal attack at a Sydney beach since 1963.

UK newspaper The Sun said Mr Nellist was an ex-RAF serviceman who was getting ready to marry his girlfriend Jessie Ho.

"Him and Jessie were due to get married last year but that got put off because of COVID," The Sun cited a close friend as saying.

"It's just horrendous. We spent most of yesterday just hoping and praying it wasn't him. It's still incredibly raw."

Mr Nellist reportedly arrived in Australia about six years ago after his RAF service ended.

The Queens Hotel in Penzance, Cornwell, where Mr Nellist once worked said staff were shocked and saddened by the news and sent their prayers to his family and girlfriend.

"Simon was a wonderful man who worked here for several years before moving to Australia - he was a valued member of staff and was always popular with guests and fellow team members," it said in a Facebook post.

Beaches between Bondi and Cronulla were immediately shut in the wake of his death as authorities watched for sharks in the area, using drones and jetski patrols.

On Thursday evening, NSW Police, Randwick City Council lifeguards and the Department of Primary Industries cleared all 13 beaches to re-open on Friday after no more sharks were seen.

The department has installed six SMART drumlines between Little Bay and Malabar as part of its shark incident response plan.

"Smart drumlines have really proven to be extremely successful and also tagging sharks to know exactly where they are and using our smart shark app, along with ... monitoring with drones," Randwick Mayor Dylan Parker said.

SMART drumlines are a new technology that allows target sharks to be intercepted beyond the surf break.

"We will continue to work really hard to make sure that people feel safe at all of our beaches," Mr Saunders said.

NSW Premier Dominic Perrottet said Mr Nellist's death was a "horrific tragedy" and extended his sympathies to his family.

"It's a reminder to us all of the fragility of life," the premier said.

Matt Thistlethwaite, the federal member for Kingsford Smith which covers beaches in the Randwick council area, said the death had sent shockwaves through the local community.

The swimming spot at Buchan Point was "increasingly popular", he said.

A local ocean swim race, the Malabar Magic Ocean Swim, planned for Sunday has been cancelled out of respect for the swimmer and his family.

Australian Associated Press