Friends have spoken out after Mercury Psillakis was fiercely mauled to death by a shark while surfing out in Australia.

A great white shark caused pandemonium over the weekend after coming close to the shores of Sydney’s Northern Beaches just after 10 am on Saturday (Sept 6).

Mercury Psillakis, 57, was bitten in half in a brutal attack after the shark appeared.

Psillakis’ surfboard was cut in half by the shark in the attack, and the surfer lost both of his legs before being pronounced dead.

Witnesses at the beach did their best to grab the surfer and get him to shore, attempting to salvage parts of his body and get it to the sands of the Long Reef Beach.

A witness at the scene, Mark Morgenthal, said that the shark appeared to be huge and spoke to Sky News about the incident.

Psillakis immediately lost both of his legs in the shark attack according to witnesses (ABC Net News)

He said: “There was a guy screaming, ‘I don’t want to get bitten, I don’t want to get bitten, don’t bite me.’

“Then I saw the tail fin come up and start kicking, and the distance between the dorsal fin and the tail fin looked to be about four meters, so it actually looked like a six-meter shark.”

As well as this, Psillakis’ close friend and former pro surfer, Toby Martin, spoke of the heroic final act his friend made before his death.

Martin came to the beach alongside Psillakis’ wife Maria after the incident and spoke to the Daily Telegraph about how his friend attempted to warn others about the shark and group them together for safety.

He also spoke out about just how vicious the attack was.

He said: “He was at the back of the pack still trying to get everyone together when the shark just lined him up.

“It came straight from behind and breached and dropped straight on him. It’s the worst-case scenario.

“They normally come from the side, but this one came straight from behind, breached and dropped on him. It was so quick.”

According to an ABC news report, Martin also reflected on the heartbreak of the loss of his friend and commended him for his determination to protect others.

Former pro surfer Toby Martin praised his now deceased friend (ABC News: Monish Nand)

He added: “A really deep loss for us on the eve of Father’s Day for an avid surfer, loving father, loving husband, great son and great person.

“[He] was just doing what he wanted to do, in a place where he loved doing it.

“Heroic to the end…self-preservation wasn’t there, just the safety of the others was important for him.”