And You Think You Felt Cold This Weekend?

On Sunday morning, a few minutes before 9 a.m., approximately a dozen giddy New Yorkers, most of whom are middle-aged, gathered at Rockaway Beach at 67th Street. Some hugged the others when they arrived. Two women ran up the boardwalk yelling, “Woo-hoo, let’s do this.”

The group was wearing only bathing suits — board shorts, bikinis and one pieces — topped with dry jackets. It was February, and they were going in the ocean.

With temperatures in the low 30s, it wasn’t New York City’s coldest day of the year — that was Saturday, when the temperature dropped to 4 degrees, and the morning swim was canceled — but it was freezing enough that this reporter, dressed in long underwear and a parka, was shivering.

The swimmers gathered together for a quick selfie before stripping off their jackets and running toward the waves at various speeds. Some stayed in the 44-degree water for only a few seconds. Others used breathing techniques to immerse themselves for up to five minutes.

When they emerged, some sprinted for their cars, eager to head home for a quick shower. Others headed to Locals, a nearby coffee shop, where they changed into dry clothes in the bathroom before participating in a beach cleanup.

This is the New York Dippers Club, a group founded in October, that meets every morning at 9 a.m. sharp to plunge into icy cold water. (They plan to continue the practice year-round.)

It was founded by Graham Cullis, 41, a nomadic painter, who was visiting the Rockaways in the fall and wanted friends with whom to do cold water plunges. He posted a message in various Facebook groups asking people to join him.

“At first it was just me and this one guy,” Mr. Cullis said. “Within a few weeks, though, we had five, six, seven people coming regularly.” Now, around a dozen people show up on weekdays and weekends. At Thanksgiving, 70 people showed up to dip. On New Year’s Day it was 130.

The group meets (almost) regardless of temperature.

“Christmas Eve was the worst so far,” when temperatures never left the teens, said Suzie Peters, 47, a neuroscientist who lives in Rockaway Beach and has gone in the ocean every day since November 30. “Some people got frostbite. We were not ready for that cold weather.” (Now the group takes precautions like laying out towels and coats in a way that allows them to put them back on more quickly. Additionally, neoprene caps and booties are encouraged.)

Cold plunges have been having a moment, thanks to wellness practitioners like Wim Hof and celebrities including Lizzo and Kendall Jenner, who have posted about the practice on social media. While the science is mixed, anecdotally, practitioners believe it helps with mental clarity, stress and depression. Others say physical benefits include pain management and weight loss (the science is also mixed on this).

This winter, cold water therapy groups have popped up across the world to make the practice more consistent. For some people, having a group means they will stick to their goals of cold plunging daily or a few times a week.

It’s safer too. Cold plunging can lead to hypothermia and an increased risk of arrhythmias and heart attacks, hyperventilation and drowning. For many, it feels safer to do it with other people around in case help is needed.

Katherine Ragazzino, 46, a retired marine who also lives in the Rockaways, has taken it upon herself to make sure everyone in the New York Dippers Club, especially newcomers, are exercising precautions like checking in with their doctor before starting the practice.

“They call me Captain Rizzo,” she said, laughing. “Sometimes I don’t even go into the water so I can help warm people up after they get out.” (Still, on Sunday she celebrated her 100th dip.)

She said made the call to cancel Saturday morning’s dip — it was too cold even for these cold plungers. “I didn’t feel it was safe. We don’t need to be heroes here. It’s not a competition.”

Last week Marianne Bertini, 62, a retired public-school teacher who now owns a gluten-free bakery in the Rockaways, had to help a man who was new to the group and feeling particularly “macho,” as she put it. “He dove headfirst into the water. You can’t do that, especially if you are new, and he kept shivering,” she said. “We all kind of huddled around him until he got warm again.”

Alex Kerkhoff, 30, who works for a tech company in Montreal, wanted to start cold plunging at Verdun Beach, on the St. Lawrence River. “For me I get this brain fog looking at screens all the time, so when I do the ice plunge it completely clears away the stress and anxiety,” he said.

But the water is so icy there, it requires making holes with hammers and drills before jumping in. “The water is only five feet deep, so you probably aren’t going to drown, but it’s still probably not the best idea to jump in that river in the winter by yourself,” he said.

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.”

He uses the cold plunge a few times a week, and he invites friends over to join him, either during the week or the weekend. “I had three friends from Connecticut visiting, and they were all excited to experience it,” he said. “It was so funny to see their faces.”

Other people have been less successful in recruiting plunge buddies.

Tim Cahalin, 46, a furniture designer who lives in Stockton, N.J., regularly jumps into tributaries of the Delaware River. “Honestly, it’s kind of like a dare thing for me,” he said. “It’s like, ‘How long can I hold this?’”

While he’s had friends express interest in joining him in theory, when the time comes, they chicken out or don’t make it a priority. As he put it, “I’ve learned that not too many people actually enjoy that activity.”