What is the origin of these annual polar plunges? Or is this some form of communal insanity which strikes specific communities? According to participants, ice swimming is possible in a water at 0 °C 'because the freezing of water releases heat, so that the water does not refreeze instantly."
Does it make them feel better?
There are strong traditions for ice swimming and dousing with cold water in Russia and Finland.
In Russia they are done for health benefits, as a ritual of the Orthodox Church for the feast of the Baptism of Our Lord, and for sports. Such club members are called "walruses" (Russian: моржи) instead of "polar bears", Wikipedia tells us.
The members of Canadian and American "polar bear clubs" go outdoor bathing or swimming in the middle of winter. "Polar Plunges" or "Polar Bear Plunges" are often also conducted as fund-raisers for charity, notably the Special Olympics, these days.
The oldest ice swimming club in the United States is the L Street Brownies of South Boston, Massachusetts, who also hold their annual polar plunge on New Year's Day.
And it''s not a strictly 'nordic' thing. The Chinese and Japanese also are enthusiastic participants. Haven't heard of any Africans voluntarily participating in this madness, but then, frozen lakes and streams are hard to find in Africa. In Harbin, northern China, as many as 200,000 registered swimmers take their plunge into an ice river hole of about 25m by 10m.
I have always wanted to do a follow-up story as to how many of these people end up in hospital requiring treatment for hypothermia. Never seen any but they must occur: in Dokkum just this past weekend, twenty kids were overly enthusiastic when testing the ice, and fell in - and had to be rushed to hospital for hypothermia problems. The effects of exposure to freezing water on the human body are well known.
So why do they still do it?