But the air in the mountains around a glacier lake seems to carry threats to everyone, from every direction.

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The most recent, in May, involved him swimming 0.75 miles (1.2km) in sub-zero temperatures in Nigards Glacier Lake in Norway.

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Before the 1960s Imja was a glacier, but a recent temperature increase in the Himalayan region melted it into a substantial lake, which glistens under the shadow of the awe-inspiring Everest range.

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