we go to arosa in switzerland, hs where each and every morning david knittel and others do something rtainly wouldn't, although you might. david insists it is the best thing imaginable for body and soul. >> i have to pysch myself up for it every morning. it is never pleasant or warm. it is almost, like, when am i doing? i'm not even awake. but then i go in and my mind switches off and i feel my whole body and it's calm. it's great. ♪ >> david knittel takes a dip in these icy waters around 7:00 every morning. but first, the layer of ice that formed overnight has to be removed. untersee lake is in the village of arosa, nestled high up in the swiss alps, 1700 meters above sea level. people can swim in the lake year-round, free of charge. today it's 1 degree celsius on the surface of the water. below, it's about 3 degrees. >> you look inwards, experience the moment, the water, the cold. you don't think about anything else. that's what's good about it. >> all the stress of daily life vanishes. you're right in the here and now. >> there's a moment of clarity, yes, a totally relaxed moment,