BEAR Grylls bares all in the latest outing of his National Geographic survival show Running Wild.
The outdoors expert strips off alongside co-star Rainn Wilson as they undergo mountaineering training in the aspen forests and alpine terrain of Utah in the US.
Bear and his funnyman pal, who found fame in America’s version of The Office, then bravely go skinny dipping in the waters of the La Sal Mountains.
Rainn reveals just how cold their swim is when he says: “That lake is about 55 degrees.
“And every part of me is shrivelled up right now. So, uh . . . sorry, ladies.”
We could tell from the photo how chilly the water was . . .
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Last month, Bear revealed he used to be a 'scrawny kid' and isn't 'naturally fit'.
The TV adventurer said: “I am not one of these people who is naturally fit, naturally super-positive. I never have been.
“I know I need motivation and encouragement.”