So he formed a group on Meetup.com in early December and asked others to join him. Now around 15 people meet every Sunday. They even have a ritual. “This guy brings music, like this tribal drum music, to get us psyched up,” Mr. Kerkhoff said. “This is the social, fun thing I now do in the winter.”
Many groups have adopted their own quirky ways of getting into the water.
Sunday Swim, a group that started a year ago and meets every Sunday at noon at Robert Moses State Park on Long Island, has the tradition of all charging into the water as a group.
“You get out of that water and you feel like an animal,” said Brendan Cooke, 23, one of the group’s founders. “We really tap into our inner warrior.” Hundreds of people show up each week, ranging from teenagers to swimmers in their 60s and 70s.
Mr. Cooke started ice plunging to manage his anger. “I didn’t have the right outlet for my stress, and I had difficulty controlling my emotions,” he said. “Cold water has taught me how to control chaos, how to tap into my inner energy. I feel way more controlled. I don’t get into arguments any more.”
Other cold water swimmers, however, are meeting much more informally in ad hoc setups.
Paul Dobrynin, a 39-year-old founder of a floor company, set up a cold plunge on his building’s roof on the west side of Manhattan. “Initially I had this cheap, small, plastic blowup pool that I put ice in,” he said. “In November I got a rubber-made 100 gallon tank that is used on farms for livestock to drink out of.”
“I run a hose through my kitchen, my bedroom, by my bed, out the window, to the roof, to the cold plunge,” he added, laughing. “It’s hilarious.”
