As a kid playing hockey on the ponds, one of the times I fell in, it was 15-20F. I was up to my neck. Tommy pulled me out. The older guys made me keep skating round and round. I was shivering so hard, I could barely skate. Soon, my jeans and jacket were frozen solid. Perfect to play goalie. I stayed and played.
I decided to upgrade my base layers. I have yak and alpaca coming. Should be fun to see which is better.