Look, I’m not going to lie: While some longtime participants in one of southeastern Connecticut’s most enduring, challenging and madcap traditions insist that plunging into icy water after a run on Jan. 1 is a refreshing and exhilarating way to start the new year, the truth is there’s a certain level of discomfort involved.

Everyone has a different pain threshold. The other day when I mentioned to my friend Sheri Lambert the ritual a couple hundred runners and I plan to embrace this Sunday – loping from downtown Mystic to Esker Point Beach in Noank and leaping into Fishers Island Sound – she shrieked in horror and then related her own experience with cold-water immersion.

“I was screaming so loud: It hurts! It hurts!” Her husband, Tim, almost had to carry her on his back.

All this after wading ankle deep – ankle deep! – across a chilly stream for a few yards.

“Sheri, I’m thinking you might not be an ideal candidate for the run-swim,” I replied.

For the uninitiated, the event (it has no formal name, entry fee, organizational affiliation or real purpose other than to proclaim shared celebratory craziness) traces its roots to Jan. 1, 1969, when three friends decided more or less spontaneously to go for a swim.

The trio – which included Amby Burfoot, then of Groton Long Point, who a year earlier had won the Boston Marathon, Lee Burbank of Mystic and Marty Valentine of Noank – drove to Esker Point, plunged in, got back in their car and rode back home.

They repeated the experience the following year, and then on Jan. 1, 1971 a handful of others joined in. At that time the group decided to start with a 5-mile run from the Pequot Avenue, Mystic home of Johnny Kelley, Amby’s high school cross-country coach who also had won the Boston Marathon and competed twice in the Olympics. In addition, instead of swimming at Esker Point they relocated to Groton Long Point’s Main Beach.

I dove in for the first time on Jan. 1, 1972, along with Bill Billing, Amby’s brother-in-law. We haven’t missed a run-swim since.

After the beloved Kell passed away five years ago the starting line shifted to downtown Mystic, and then the swim destination moved back to Esker Point.

Over the decades the event gained popularity, attracting hundreds of costume-clad runners blowing noisemakers, an equal number of spectators, and even pods of kayakers who watch the spectacle from the water.

Everyone is invited. The run kicks off at noon from the Johnny Kelley statue on West Main Street in Mystic and proceeds about 3.5 miles along Route 215 (with a detour up the steep hill at Brook Street) to Groton Long Point Road and the beach. It’s more of a shuffle than a competitive run; we stop several times to allow stragglers to catch up.

Some runners carry packs containing towels and dry clothes for the run back; others hitch rides with friends/family for the return trip; and some leave early from Esker Point to run to the start in order to have a car waiting after the plunge.

Amby will be there Sunday to repeat his 1969 inaugural baptism. He and I have been joining a group of friends who run a 7.3-mile trail course from Haley Farm in Groton to Bluff Point and back a few times a week, and we always stop at the bluff to gaze at the water.

One morning a couple weeks ago the temperature dipped into the teens and waves crashed on the rocks.

“Now that’s the kind of conditions we need this New Year’s Day,” I said.