The thing is that seasoned citizens are usually able to swim or at least float on their own. They might not be fast anymore, but they know how to tread water and don't usually panic.
I think you're right...another poster has weather conditions...all seemed fine.
Dunno on this one...really, really sad.
It's a catch 22 situation. Treading water/swimming expends energy and increases the loss of body heat which speeds up hypothermia. Having a life vest on or something that floats and clinging to it and other people is the best way to preserve body heat.
Of course the shock of the cold water would be enough to raise certain folks BP and heart rate to cardiac arrest levles.
God bless them all.