The ocean temperature here year round is 13C. When we were kids we'd body-surf. This was before O'Neil (up the road) made wetsuits for surfers/swimmers, so we'd hit the water in swim trunks and t-shirts. The trick was to wade out waste-deep to acclimate, and then move out to the surfline. We'd be in the water for about a half-hour before coming out to warm back up on the sand. Our legs were purple, and lips would be numb. Then we'd go back in for another half-hour, because our bodies were "used to the cold now!".
When we came out the second time we'd be shivering so hard we couldn't speak normally. Being kids, we thought this was hilarious. Three or four of us all huddled under our towels, our bodies shuddering for a half hour until we stopped shaking enough to get our shoes on, and walk home.
Never occured to any of us this could have been lethal. And it lead to more bad decision making later in my youth that would see me almost drown twice, not counting that rip-tide day. And yes, I found out the hard way that cold water will knock the air out of you as if you've been hit by a car. I wasn't expecting it, and I was lucky I was in shallow enough water, or I'd have been dead. The worst case of hypothermia I survived was on a rainy day hike. The air temperature that day was around 9C, and I wore no rain gear on a six-hour hike. I have no memory of the last forty-five minutes of the hike, or how I got back to my truck.
I post this because I don't think of myself of a moron, but I clearly underestimated hydrothermia, and overestimated my physical ability to overcome it. Many people have never experienced hypothermia, and cannot understand what how it deceptively engulfs people, affecting their judgement and thinking, and leading them to their deaths.
To bring this back to the subject, hypothermia will color what the survivors claim they remember, 100%. Add PTSD into the mix, and their recollections must be taken with a grain of salt.