On Fri, 18 Jan 2019 05:57:33 -0000, Paul wrote:

Commander Kinsey wrote:

Are you serious? 10 seconds? Water is never cold enough to get out
that quickly. I can swim in zero degrees C water for a couple of
hours. Humans are warm blooded. Shivering doesn't mean you're going to
die, it means you've lost 1 or 2C (out of 17C required to die) and your
body is shivering to prevent further heat loss, not to mention brown fat
cells generating heat, and of course limiting heat loss by adjusting
blood flow to the skin.

I have a small amount of experience with it.

At 68F, I've swum for two hours. Days when no one else
at the beach would go in the water. The trick is to keep
moving, and if "standing" in the water, to jog on the spot.
That helps balance the heat loss.

At 49F, I could swim about 50 feet along a dock, and barely
had enough limbs left to grab the ladder and get out.
I had a helper on the dock, ready to assist if
necessary. And that's wearing swim trunks.

49F in 1st world measurements is 9.5C. That is not cold by anyone's standards. If I swim in 15C water, I'm too warm, anything over 15C and I often stop, lie on my back and try to cool off a bit. You can't sweat underwater.

How cold were you when you got out? Were you shivering? There's no way you could have cooled down enough to shiver in 50 yards, therefore your core body temperature hadn't even dropped by 1C.