Polar bear dip not enough? There is an International Ice Swimmers Association. Swimming in ice is a dangerous sport..they must swim in only a bathing suit, goggles, and a cap with the distance being one kms.
As you get in the water your body temperature starts to drop, the cold takes your breath away..it becomes a matter of controlling your mind with the average time in the water being 15 to 20 minutes.
You can see more at their web site at http://www.internationaliceswimmers.com
Check out this video and see their challenge.