Fish, in water with rapidly falling temp. is hardly the same as putting a live bird in a freezer. i don't advocate tossing a fish into a freezer to flop around and freeze solid to the side of the Dove Bars.
I got the to the early stages of hyperthermia about 10 years ago. I got soaked while Elk hunting at 11K ft. I managed to keep my wits and hike just over a mile to camp. When I stumbled in I was shivering, exhaustion and starting to get confused. Fortunately, my friends we in camp to help. Dry cloths, warm water to sip, and I'm here today to take about it. I can honestly say I had no feeling of pain. I was/am experience enough to have know to force myself to stay calm & focused.