Diver taken by shark off Adelaide coast

ADELAIDE - A cuttlefish researcher is presumed dead after a shark took him during a diving trip off Adelaide, despite his colleagues' frantic efforts to save him.

The man and another diver were in the water off Glenelg Beach when two of their colleagues aboard a boat saw the shark approach and hauled one of the men out of the sea.

But the shark used its snout to push the other diver back into the water before his friends could grab him, a colleague of the men, who asked not to be named, said.

A search was launched immediately after the attack, which happened about 4pm CST (6.30pm NZT), and an oxygen tank and buoyancy vest were recovered.

Darkness forced emergency crews to suspend the search before the man's body was found. It will resume at first light on Thursday.

The four involved in today's attack all worked with the University of Adelaide and had been collecting cuttlefish eggs for a research project.

The university's head of earth and environmental sciences Professor Bob Hill said he knew the four, and all were experienced divers.

"I'm actually quite proud of the three of them from what I have heard... they made every attempt they could to do the right thing," Prof Hill said.

South Australian Police Acting Superintendent Jim Jeffery said police were unsure what type of shark was involved in the attack, saying the traumatised witnesses had only described it as "large".

"The indications to us are that it will be very doubtful that we will find the person alive," Supt Jeffery said.

Today's attack happened at a tyre reef about 2km off shore from Glenelg beach, 15km west of Adelaide's central business district.

And it was within a kilometre of the spot where 18-year-old Nick Peterson was killed while surfboarding with friends behind a boat.

The waters off South Australia are a favourite hunting ground of the feared great white shark, which has been blamed for several fatal attacks in recent years, including that on Mr Peterson.

Today's presumed fatality is the fifth from a shark attack in South Australia since 2000.

Local shark expert Andrew Fox said it was likely the shark was a great white -- the same type of shark blamed for the fatal attack on Mr Peterson just over eight months ago.

"As far as determining the species of shark it's very likely that, other than a bronze whaler shark, the great white shark is really the only large predatory shark that's capable of actually taking a diver," he told ABC radio.

Mr Fox said he doubted the shark involved in today's attack was the same one that took Mr Peterson.

"There's always speculation after any shark attack around the world of a rogue shark, or a shark gone bad, a shark that likes the taste of humans," he said.

"But there's actually, in the International Shark Record, there's never been any evidence that this has ever occurred."

Local boatie Keith Klemasz, who was in waters near the Glenelg tyre reef today, said he wasn't surprised a diver had been taken.

"It is crazy, they are shark bait," Mr Klemasz said.

"It's very unfortunate... but I don't think it's a good idea to dive when you have got a lot of boats out.

"It's a feeding pattern, if we are all putting berley in the water, that will attract them (sharks)".

Another boatie, Alby Dixon, said he was 100 metres from the university research boat at the time of the attack.

"I saw them diving but I didn't see any sign of distress," Mr Dixon said.

"We were that close and we didn't even realise it had happened."

- AAP