Peeing in your wetsuit, it's right up there with death and taxes as one of life's certainties. Even so, our civil sides don't like to talk about it; especially that great feeling it gives you on a cold dive. It warms you right up from the inside out---or does it?
I've been reading that despite what you might think, peeing in your wetsuit will not actually warm you up. What happens is that the warm urine opens up the blood vessels near your skin's surface. These blood vessels think they are no longer cold and relax. Then, shortly thereafter, the warm pee gets washed away and cold water returns. The blood vessels are no longer constricted, so they very quickly allow your warmth to be taken away before they realize it's cold again and constrict.
This constriction, by the way, is what leads to numbness. It's your body's way of protecting its vitals, by restricting blood flow to the less-important extremities.
This peeing myth was certainly news to me. It's something to remember next time I'm tempted to pee in my wetsuit on a cold dive. But hey, who am I kidding? I'm gonna do it anyway.