Simply putting canopies on dinghies would have saved a lot of chaps, I reckon...never understood why they didn't.
Probably because the effects of wind chill and hypothermia weren't widely understood at the time.
The only ones that put humans through extensive hypothermia research (at lower temperatures) were the Nazis at Dachau. The Nazis immersed their subjects into vats of ice water at sub-zero temperatures, or left them out to freeze in the winter cold. As the prisoners became unconscious, the so-called Nazi 'doctors' meticulously recorded the changes in their body temperature, heart rate, muscle response, and other characteristics.
I've modified that quote, the original is even more graphic and repellant.
Thank you, regle et al., for blasting some of those Nazi swine off the face of the earth.
The best invention we could have had in WW2 would have been anything which improved inteliigence about high value targets and a method of concentrating Bomber Commands assets more productively than they were in the earlier years.