I was on a whitewater rafting trip when I was in my 30s and in good shape. At one point, we had stopped for lunch and the guide told us that we could jump into a race on a section of the river. Of course, I jumped in. The water was so cold! My breathing became labored and thought I was going to have a heart attack. I did not hear anyone else in the group, most of whom were younger and male, describe having an experience like mine.
They were in pain- but they'd never admit it.