When I'm getting ready for a tournament or fight, I go for a dip in a glacier water stream almost every day. We'll do some interval running for about 45 minutes to an hour, then go in the water immediately afterwards and try to stay in there as long as we can stand it. About 2 minutes is the longest I can stand it before I feel like my heart is going to stop and my junk is going to disappear. We go in all the way, head under water, buck-naked.
I only do this during the last month of training leading up to the fight. I wouldn't do it year-round, just during times of high-stress on the body. It's supposed to build up your heart and willpower. I definitely feel better AFTER getting out of the water, lol! It's like everything is colourful and new, and when I get home the food tastes better and I sleep like a baby. They call them "spirit baths" in my mother's community.