Martin Blackley was based at HMS Condor in Arbroath

Martin Blackley, 26, of Aultbea, drowned while working at a fish pen in Loch Ewe, Wester Ross, in May 2002.

Sheriff Desmond Leslie said Seahorse Aquaculture "ignored" regulations by allowing Mr Blackley to carry out dives in exchange for a �300 dry suit.

The commando based in Arbroath was on sick leave after injuring a leg.

Marine Harvest, the company whose fish farm Seahorse Aquaculture had been contracted to work on, have also been criticised.

Sheriff Leslie presided over a fatal accident inquiry held into Mr Blackley's death last September.

He said that at the time of the accident Marine Harvest had failed to "police its health and safety procedures and practices adequately".

In his determination, the sheriff said that Mr Blackley was swimming and had also taken up diving to maintain his fitness during his sick leave.

I offer my deepest sympathies to his family who attended the inquiry with great diligence and showed quiet dignity throughout Sheriff Desmond Leslie

In exchange for a dry suit provided by James Bell, an employee of Seahorse Aquaculture and the son of the firm's owner, Mr Blackley agreed to carry out dives for the company.

On the day of the accident he was diving to remove dead fish from a pen.

An hour after entering the water, Mr Bell and another worker became concerned for Mr Blackley's safety.

The marine was recovered with a rope entwined across his chest and oxygen cylinder.

His mouthpiece and mask were off his face.

Sheriff Leslie said Mr Blackley was not provided with a full face mask suitable for the type of diving he was undertaking, or with a life line.

There was no two-way communication with the surface vessel monitoring the dive and the dive team was "inadequate and under-equipped", said the sheriff in his determination.

This led to a "lack of supervision and the absence of a fully equipped standby diver prepared for emergencies", he said.