Paul de Gelder knows exactly what it's like to come under attack from one of the sea's most deadly predators.

It was only six years ago when Mr de Gelder became the first person to be attacked by a shark in Sydney Harbour in 60 years.

Despite losing his right leg and right hand as a consequence of the attack, Mr de Gelder considers himself "lucky".

A recreational scallop diver became the latest person to be attacked by a shark in Australian waters when he was killed by a reportedly about 4.57 metre shark in Tasmania on Saturday.

Tasmanian police have not released the identity of the man, but said he was aged in his late 40s and from Kingston area, south of Hobart.

It comes less than a week after Australian surfer Mick Fanning had a close encounter with a shark, also believed to be a great white, while competing in the final of the World Surf League's Jefferys Bay final in South Africa.

The incident was captured live on television.

Mr de Gelder says the shark attack was "like living my worst nightmare".

"It was February 11, 2009 and it was coming to the end of summer.

"It was 7 in the morning and it was still all through the harbour, which is pretty murky so you can't see well.

"When I first saw it, it was attached to my leg but I didn't feel any pain.

"I thought I was dead and that I wouldn't get out alive.

"But I was phenomenally lucky because if it had of nicked my femoral artery, I would have bled out and died before I got out of the water.

"It was lucky and unlucky at the same time."

Mr de Gelder said scallop and abalone diving was "inherently dangerous" and urged both recreational and commercial fisherman to exercise caution.