A missing diver has been rescued unharmed after a ten-hour search on land, sea and air.

The operation began after the Ivan Doychev was reported missing from a scallop diving boat off South Ronaldsay in Orkney on Wednesday.

He had already been in the water for an hour when three RNLI lifeboats were dispatched at 5.20pm, along with two coastguard helicopters, onshore search teams and four local vessels.

Almost ten hours later a Russian yacht passing through the Pentland Firth spotted the diver swimming towards them a few miles east of Duncansby Head.

The crew of the Yunyi Baltiets took him aboard and transferred him to an RNLI lifeboat, which took him ashore.

Mr Doychev posed for a picture at Thurso lifeboat station before being taken to Caithness General Hospital in Wick for treatment.

Thurso RNLI coxswain Wing Munro said: "He is a very lucky chap to be still alive after being about 11 hours in the water in the Pentland Firth as it is very chilly.

"He had all his diving gear on, that would have helped a lot, and probably very good quality, thick gear.

"The sailing ship that picked him up, he saw it coming and swam towards it himself. He still had a bit of strength left.

"He is a very lucky man as it's not easy to see someone in the dark, you have only got a couple of search lights and if the search light is not in the right place you could miss it easily.

"He is also lucky that anybody saw him at that time of the morning."

The Yunyi Baltiets, a 160ft-long sail training boat, is travelling from St Petersburg to Wester Ross with 15 crew and 32 Russian naval cadets aboard.

They are due to participate in Loch Ewe 75 this weekend, an exhibition of ships which were part of the Arctic Convoys during the Second World War.

On Monday, surfer Matthew Bryce was rescued after spending 32 hours at sea clinging to his surfboard.

He was found by a coastguard helicopter 13 miles off the coast of West Port Beach, Argyll, where he had set off from the day before.

The 22-year-old was airlifted to Ulster Hospital in Belfast with hypothermia and is thought to be recovering.