Emergency services searching for a surfer believed to have been killed in a shark attack off South Australia's Eyre Peninsula say they have recovered the man's board, and that several people witnessed the incident.

The 46-year-old man from Elliston was surfing at Walkers Rocks Beach on the Great Australian Bight when he was attacked an estimated 30 to 50 metres offshore, and is now missing.

Police and the State Emergency Service (SES) were called to the spot, about 7 kilometres north of Elliston, after 10am.

The SES said the "well-known" local was believed to have died in the attack and a search involving police and community members was underway.

More than half a dozen boats, as well as jet skis, searched the waters where he was last seen before stopping for the night.

Authorities said the search would resume at first light on Sunday morning.

Streaky Bay SES unit manager Trevlyn Smith said he had been told there were perhaps as many as 16 other people in the vicinity at the time, some of whom witnessed the attack.

"There were obviously several people in the water and from what I can hear there were witnesses that saw evidence of the attack," he said.

"It was fairly close to the shore I believe."

No-one else was injured in the incident, but Mr Smith said the man's surfboard had been retrieved.

"We were told that they had recovered the surfboard, by [a searcher on] a jetski as I understand, and then that was transferred onto one of the local vessels," he said.

"We've got a missing person, they've already got the surfboard ... we're just looking for anything that relates to [that] person."

Community left 'devastated'

Mr Smith said there was "absolute shock and dismay" at what had happened.

He said the man was "well known" in the community, and abalone diver Jonas Woolford said, "locals would be devastated".

"It would shake them, totally, it's full on. We haven't had a shark attack here on this coastline for over 20 years, fortunately," he said.

"If you lose someone from the community, it would really hurt."

Mr Woolford, who joined the search operation, was bringing tourists back from Flinders Island about 35 kilometres west of Elliston when he noticed something was wrong.

"As I pulled up there was a lot of commotion going on at the boat ramp and then I learnt that there had been a shark attack," he said.

"Walkers Rocks — it's quite close to shore and not really the place you would expect, like there's not too much deep water around, so yeah it's concerning, really concerning."

The remote area is popular with surfers and divers, but the broader Great Australian Bight has a history of shark incidents.

"Shark attacks are very rare, fortunately, but … the number of great white sharks is increasing," Mr Woolford said.

"Us as divers, we're seeing more and more and it's well known that, along the whole southern coastline of Australia, there's more interactions for sure."

Elliston is about 650 kilometres from Adelaide, and the Bight is notorious for the presence of sharks — including great whites — in its waters.

Google Maps marks a "shark breeding ground" just south of Walkers Rocks Beach, while Port Lincoln towards the southern tip of Eyre Peninsula is home to cage diving tour operators.

While fatal shark attacks have occurred with much greater frequency in other states in recent years, the Bight was the site of two deadly attacks in as many days in 2000.

On September 25 of that year, 17-year-old Jevan Wright was killed while surfing at Elliston — a day after 25-year-old New Zealander Cameron Bayes was fatally attacked, while on his honeymoon, at Cactus Beach near Penong.

Less than two years later, Paul Buckland was killed near Ceduna, and several more deadly shark encounters have occurred in SA waters since then, including the death of Sam Kellett in 2014.

The 28-year-old teacher was preparing for a spear-fishing competition when he was taken by a shark off Goldsmith Beach near Edithburgh on Yorke Peninsula.

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