Victorian man killed in SA shark attack

A man from regional Victoria who went missing while snorkelling off the South Australian coast is believed to have been killed by a shark.

Police have discovered a damaged wetsuit and flippers which are thought to have belonged to the 32-year-old while searching waters off Surfers Way near Port Macdonnell, in the state's lower southeast, on Friday morning.

It comes after a shark was spotted in the area on Thursday by a police helicopter.

"Tragically, police suspect the Victorian man has been the victim of a shark attack," SA Police said in a statement.

Police were contacted on Thursday after the man's disappearance and launched a search assisted by SES crews, Fisheries SA and local volunteers.

The air and sea search is now being scaled back and police will prepare a report for the coroner.