The diver, who was not from Orkney, was unconscious on the dive-boat when the Stromness lifeboat and Coastguard rescue team arrived.

He was taken ashore while attempts were made to revive him, but was pronounced dead by ambulance crew at Houton Pier.

The police, who have yet to name the diver, said an investigation was under way and a report would be submitted to the Procurator Fiscal.