cold swim

I've heard of the polar plunge in many communities where people raise money by jumping into the cold water but they quickly get out and end up in a hot tub.  Once a year and they're done.  In Russia, there's a group of people who do this every week and they stay in for an extended swim.  They say that it improves their health.  It's so cold that they have to cut a square hole in the ice just to get to the water.  winter swimmers