Yeah, I don't think your core temp drops in three minutes, it's the temp in your limbs. In which case, it's harder and harder to move them... ie tread water or stay afloat. Or get up onto the ice if you fell through. That's the part that kills.

To back up that statement, look at your own statement under the "1-10-1" tab. Funny graph too - apparently a fat woman can just pretend she's a whale for 5 hours and not be hypothermic... a fat guy can pretend for less time... does that make much sense (scratching head)?