The force said that it attended the scene with ambulance services following a call at 5.20pm after the diver had been pulled from the water, but that he had been pronounced dead at the scene.
The police were undertaking an initial investigation with the Health & Safety Executive (HSE) on behalf of the coroner.
In Orkney, meanwhile, an HSE investigation into a diver's death seven years ago has resulted in a boat-owner being sentenced to carry out 200 hours of unpaid work.
Appearing at Kirkwall Sheriff Court, Shaun Geddes admitted to breaching health & safety laws in connection with the death in March 2012.
Geddes was skippering his boat the Hildona when 33-year-old self-employed scallop-diver Rodney MacLean failed to surface from a dive. His disappearance sparked an extensive search-and-rescue operation, though his body was not found until November.
Following the subsequent investigation, Geddes was charged with breaches including failure to ensure that diving-plan risk assessments were prepared or safety briefings provided. The court also heard that he had failed to ensure that working divers held appropriate qualifications or medical certificates, according to a report in Scotland’s Press & Journal.
“Today’s outcome will highlight the need for all parties involved in commercial diving projects to keep the health and safety of divers to the fore,” said HSE inspector Bill Chilton, following the verdict. He added that he hoped the sentence would “send a strong message to the shellfish-diving industry that all individuals have a duty to plan and carry out work properly in order to protect workers”.