A 4.2 metre great white shark was spotted in the water just after a man disappeared at a popular South Australian surfing spot.
Emergency services on Wednesday continued their search for any trace of the 55-year-old man who was surfing at Granites Beach, south of Streaky Bay on the Eyre Peninsula, where he was attacked on Tuesday morning.
It is the state's second fatal attack in six months.
The man's surfboard was all that remained of the attack, witnesses said.
Local surfer Jeff Schmucker was about to get into the water when he heard the commotion.
"All the kids were on the rocks waving at me and yelling and I knew there was something wrong well before we even got there," he told ABC Radio on Wednesday.
Mr Schmucker, who has worked as a commercial fisherman in the area for decades, jumped on his jetski and rode to the spot where the man had been surfing.
After a moment, a 4.2 metre great white appeared, he said, which he followed for a while as it circled.
"I've seen many great whites in my fishing career," Mr Schmucker said.
"It just rammed home events over the last 20 or 30 years."
The incident follows a fatal attack on another surfer at Walkers Rock Beach in May, just 100km down the coast.
The body of 46-year-old teacher Simon Baccanello has never been recovered.
Earlier this month, 64-year-old Pamela Cook suffered serious leg injuries when she was bitten by a shark at Beachport on the state's southeast coast.
"There's too many sharks to actually think that surfing is anywhere near safe on the West Coast," Mr Schmucker said.
Premier Peter Malinauskas called the attack an "awful tragedy".
"Our thoughts are with the family of the victim of the shark attack," he told reporters.
"On all accounts it was a brutal one that clearly has dire consequences."
Asked whether the government would consider implementing regular shark patrols on the West Coast, he said there were big logistical challenges in the way.
"This is a tragic accident," he said.
"There's not too much that anyone can do about it."
Shark expert Andrew Fox said while Mr Schmucker's hypothesis that banning gill nets in fishing had reduced the numbers of great whites caught as bycatch, the reduction in incidental killing was not enough to make a significant contribution to the population.
"From what we know about our genetic studies and micro-capture analysis is that there is a limited amount of sharks," he told ABC Radio.
"That's the reason why they're listed as vulnerable on the endangered species list with the (international conservation) red list.
"We need to base any talk about shark conservation or culling on real scientific reasons."
Police put the search for the man on hold in the afternoon due to unfavourable oceanic conditions and said they will reassess on Thursday morning.
