Ivan Doychev, 40, said the sight of helicopters and boats searching for him also helped keep him going, as he drifted in the Pentland Firth off the far north of Scotland.
A major search operation was launched after Mr Doychev was reported missing from the dive boat Fair Morn at 5.20pm on Wednesday, off Burwick in Orkney.
He was spotted in the water at 3.15am on Thursday by the crew of Russian sail training vessel Yunyi Baltiets, and managed to swim towards them.
Mr Doychev, a professional diver from Bulgaria, said it was the strong tide which pushed him out of the islands.
He told The Press and Journal: “The first hour was terrible, the tide pushed me out and out and out - I was in the middle of the sea. The tides changed and I started to go back.
“I am very appreciative. I could see the choppers and boats. They were far away but I could see them so I knew they were looking for me, which kept me going.”
The diver, who lives in Orkney, added: “Maybe I’m lucky. All I did was stay positive. I did not panic. I knew not to panic and just keep swimming.”
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The crew of the Yunyi Baltiets pulled the diver from the sea and he was then transferred to Thurso RNLI lifeboat at 4am and taken to shore on the mainland.
He appeared to be in reasonable health but was taken to hospital in Wick for a check-up.
RNLI Thurso 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 search operation involved RNLI lifeboats from Thurso, Longhope and Stromness and two Coastguard rescue helicopters.
Shoreline searches were also carried out by Duncansby, Scrabster, Hoy and St Margaret’s Hope Coastguard teams, while radio broadcasts were made to all vessels in the area to keep a lookout for a missing diver.
Gary Harris, who was co-ordinating the incident in Shetland Coastguard operations centre, said: “During search operations at sea, it’s incredibly challenging to spot a head in the water, especially at night.
“The diver was very fortunate to be spotted by the crew on the sail training vessel Yunyi Baltiets and taken aboard safely.”