Sydney beaches reopen after shark attack victim named as diving instructor Simon Nellist

The 35-year-old man from Wolli Creek was named by the ABC on Thursday evening as certified diving instructor Nellist.

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

The beaches, along with some others further north and south, were closed for 24 hours after the attack. The DPI also deployed six Smart drumlines from Little Bay Beach to Long Bay.

The search for human remains resumed on Thursday using drones as well as lifesavers on jetskis and on the sand. Water police and PolAir also patrolled the area.

Surf lifesavers used drones and jetskis to check the surrounding area for further shark sightings on Thursday, Randwick council said.

It was the first fatal shark attack in Sydney waters since 1963.

A witness told Nine News he had seen a four-and-a-half metre great white shark attack Nellist.

Marine scientist with Macquarie University Dr Vanessa Pirotta told ABC News the species could be a great white shark because of its behaviour during the attack and its large size. She said it was unlikely the shark responsible would be found by authorities.

Bond University shark attack expert Dr Daryl McPhee called for calm and media restraint as authorities continued investigating.

Additional reporting Australian Associated Press