Depends what you mean by withstand! Once your body temperature goes down even a few degrees you go into hypothermia which is eventually fatal if you don’t warm up quickly. However, there are extreme examples of people going to based on what I read down to only 13C when submerged into cold water and have lived through the experience.
My guess the lower limit is a body temperature down to freezing. Once freezing occurs ice crystals will destroy your cells (that is what frost bite is).
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