A cute and handsome 35-year-old British man has been named as the victim of Sydney's first fatal shark attack in nearly 60 years. The attack was caught on video.
Police have not yet formally identified the victim and his family have not commented.
Australian authorities are still searching for the great white shark, with swimmers banned from the water and most city beaches shut after Wednesday's attack.
Mr Nellist - who was a diving instructor - was mauled by a great white shark just off Little Bay in east Sydney. He was a member of the city's Scuba Diving Social Club and a regular swimmer at the beach.
A UK foreign office spokesperson said consular staff were in touch with New South Wales Police. "We are supporting the family of a British man and our thoughts are with them at this difficult time," the spokesperson said.
Shark attacks in Sydney are uncommon because the city has long had nets and other deterrents in its waters.
On Thursday, surf lifesavers on jet skis patrolled a 25km (15.5 mile) stretch of water from Bondi in the city's east to Cronulla in the south to find the shark. Authorities are also using helicopters and drones.
The state government said its shark experts had estimated the predator to be a great white shark "at least three metres" in length based on footage of the incident taken by a member of the public.
Several passers-by who witnessed the scene have described a vicious and frenzied attack.
"The person was swimming and a shark came and attacked them vertically," Kris Linto told Nine News.
"We heard a yell and turned around, it looked like a car had landed in the water, a big splash then the shark."
One man recounted how he had been fishing on the rocks when he saw the swimmer get dragged under.
"It was terrible. I am shaking. I keep vomiting. It's very, very upsetting," he told ABC News.
Authorities managed to retrieve body parts from the water two hours after the attack.
The area's state MP Michael Daley said locals were shaken by the "horrific" incident. The victim had been a regular visitor. "He came here and swam nearly every day," he told the ABC.
"It's a beautiful day at one of Sydney's most beautiful beaches, but there's a real dark pall hanging over our community today," he said.
Simon Nellist: Sydney shark victim named locally as British man
Simon Nellist died in the city's first fatal shark attack in almost 60 years, a friend says.