In the United States, polar bear plunges or ice swimming aren't necessarily held to welcome in the new year nor are they exclusive for nudists. One of the oldest annual aquatic freeze-athon in this country takes place in Boston, Massachusetts, and began in 1904. Most are associated with fundraising for charitable organizations. One of the largest events is held at Sandy Point State Park in Maryland. Sponsored by the Maryland State Police, "Plungapalooza" supports Special Olympics and recently collected almost $2.2 million USD with more than 8,500 participants.
In Northern Europe and throughout Russia, ice-swimming is often performed as part of the sauna tradition and is exclusively nude. Finland has the highest per capita participation with an ice-swimming season that commences in October every year and continues through mid-March. In Russia, where ice-swimmers are referred to as walruses and not polar bears, swimming naked in winter is done for health reasons, sports training and for religious (Russian Orthodox) purposes, especially surrounding the Feast of the Baptism of Our Lord.
In Central Europe (Germany, Netherlands, northern France, etc.), winter swims or plunges don't always involve ice or arctic creatures (polar bears or walruses). More likely, the activity consists of plunging nude into a body of water at or just above freezing temperatures. These swims often occur in places where public nudity isn't specifically allowed by law or custom. Just as skinny-dipping is tolerated in summer, the same level of acceptance is extended in the winter chill.
China boasts a national registry of naturists winter swimmers that numbers more than a quarter of a million members. This tradition began in that country after the communists gained control of the mainland in the late 1940s. Most Chinese use this as a part of their health regimen and clubs organized for this purpose are gaining in popularity.
No matter the reason people engage in this winter practice, most agree that it involves a certain level of courage and daring to figuratively "take the plunge." I've never participated in an outdoor swim on New Year's Day, preferring instead to satisfy my nude aquatic urges in a heated indoor pool. However, should I decide to welcome a new year swimming naked, I think I'll start with a trip to a place in the Southern Hemisphere or at the very least, closer to the Equator.
Peace! Get naked. Enjoy!