A South African completed one of the world's most extreme ice swims on Thursday in a Scottish loch, a spokesman for the International Ice Swimming Association said.

Ram Barkai swam 1.6km (one mile) across Loch Faskally, with a water temperature of two degrees Celsius, near Pitlochry in the Scottish Highlands.

Fellow South African Gavin Pike swam 1.4km. An official ice swim is one mile in water with a temperature of five degrees Celsius or lower. The air temperature was minus two degrees.

Association spokesman Craig Doonan said on Friday that the men spent 35 minutes in the water wearing nothing but Speedo costumes, caps and goggles.

Barkai holds a Guinness World Record for swimming a kilometre in an Antarctic lake with a temperature of one degree Celsius in 2008. His feat will be featured this year in a TV episode of Stan Lee's Superhumans, for his ability to swim in life threateningly cold water.

After the swim Barkai said he was numb and could barely move.

"I knew we were truly pushing our limits. It was a very hard swim, probably my toughest yet," Barkai said.

Pike said the impact of the cold was "profound".

"I was in very bad shape when I got out, but we both managed to recover under the supervision of a doctor and our support team."

Barkai, the founder of the International Ice Swimming Association, said his next challenge was an international relay swim across the Bering Strait between Russia and the USA in July. He would be joined by fellow South African extreme swimmers Ryan Stramrood, Toks Viviers, Kieron Palframan and Andrew Chin.

On New Year's Eve Barkai swam a mile in six degree water in Mulroy Bay, Northern Ireland, alongside Irish long distance swimmers Anne-Marie Ward and Nuala Moore.