by James Hubbard, M.D., M.P.H.

Real case. A doctor falls through an ice hole while cross-country skiing. They find her body many yards away. It’s been under the ice for over an hour. She is resuscitated. After the ICU, she spends many months in rehab, but in a year she’s back to practicing medicine.

A snowmobile accident submerges a man in icy water for an hour. He lives, with no apparent brain damage.

It’s rare, but it happens. In normal circumstances the brain can’t go without new oxygen for over six minutes without developing significant damage. How can some people survive an hour of total submersion–seemingly drowned in cold water?

Part of the answer is that the rapid cooling can trigger the mammalian dive reflex.

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