Insulation! i.e. fat, that's what you'd need. And youth. Not having either, I think I'd die of sheer misery on the way down, or cardiac arrest on hitting the freezing water. But I'd have given me more of a chance when I was young, even though I wasn't any fatter. I'm sure some of those younger ones given up for dead were not actually dead, but suffering from hypothermia. But in those days, even if they'd heaved them aboard and tried to resuscitate them, they'd have probably killed them in their efforts to warm them up, as the cold blood re-circulated back to the heart kills mercilessly. The 'Japanese' survivor who stunned Lowe in Boat 14 by reviving rapidly and rowing strenuously, was probably a young man, used to being cold, with plenty of natural insulation. I think Katherine Hepburn was simply obdurate. Jane Fonda, who worked with her in 'On Golden Pond', said she was extremely unforgiving of people she termed 'soggy' for being nervous about taking physical chances. Jane gulped, and did a back-flip into icy water, and credited Katherine for having made her do it. She didn't do it again, though.