Seth Baetzold loves to swim in cold, even freezing water.

“It’s really refreshing,” he says. “You jump in, and it gives you this kind of cold shock.”

Baetzold, 28, from Maplewood, has swum in the waters of an ice-covered Vermont lake in February.

He’s done a 24-mile, 50-degree swim in the St. Croix River in October.

“Some of it is controlled hypothermia in a way,” says Michael Miller from Minneapolis — a fellow swimmer. “You just need to not let it bother you.”

Here in Minnesota, we might be used to the cold, but we don’t always seek it.  

For these swimmers, it’s toughness over temperature — and mind over matter.

“Just being cooled off and your body’s heating up, but it’s being cooled by the water,” Baetzold explains. “After a while, I start swimming, I heat up, and it just feels amazing.”

His latest aquatic adventure: a 48-mile relay swim in August, from Split Rock Lighthouse to Duluth’s Canal Park within 24 hours.

Miller is one of the six cold water swimmers who took part.

By day and night, each participant took four one-hour shifts, without a wetsuit — dealing with the cold, six-foot waves, and little sleep.

“It’s a wonderful way to experience nature and especially Lake Superior,” Miller says. “The description is like a washing machine at certain points in time.”

“The wind and the waves started to get four or six feet of waves,” Baetzold adds. “The boat was rocking, and it was a little bit tough to swim in it.”

The swimmers were watched over carefully by crews in kayaks, sailboats and zodiacs.

Experts say a swim like this might not have been possible just a few decades ago.

“We’re in an era now where we have many more years where it would be tolerable, and fewer and fewer where it would be told cold to do this,” says Jay Austin, a U of M Duluth physics and astronomy professor who’s also been studying about changes in Lake Superior.

He says warmer air over the lake, especially in winter, is leading to warmer weather temperatures.

“We’re seeing significantly warmer waters now than we were 20 to 30 years ago, and that is entirely a response to climate change,” Austin says. “Just a few years ago, we had a year where it was in the 40s at this time of year, and that was a bit more common 20 or 30 years ago.”

Hamline University’s Center for Global Environmental Education says Lake Superior’s temperature has risen about five degrees since the late 1990s, and is one of the fastest warming lakes in the world.  

The center, which provided the boats to watch over the swimmers, is making a documentary about the relay and how Lake Superior is changing.

Baetzold says he’s noticed the difference, too.

“People have told me stories from 57 years ago when they’d swim in it, and it’d be frigidly cold everywhere,” he says. “And now, there’s warm spots in it, algae blooms. I’ve even gotten in it when it’s 70 degrees on the 4th of July.”

Baetzold says conditions were much chillier this time.

The team finished in about 23 hours.

He hopes this swim will raise awareness about the lake’s condition, but agrees that cold-weather swimming isn’t for everyone.

“Whenever you do anything that’s out of the norm, people think you’re crazy,” he smiles. “But I enjoy it. Maybe I think they’re crazy for not doing anything like this.”

The team has a total of 75 years of experience with marathon swims in oceans, rivers and large lakes.

Miller emphasizes everyone should take precautions when taking to the water in Lake Superior.

“We should encourage more careful swimming, not more swimming,” he says.  

Baetzold says his next challenge will be to attempt to swim the English Channel — about 21 miles across — in July 2025, where the temperature can be as cold as 56 degrees.

Not a problem for him, he says.

“It’s kind of like a cold day when you come in and heat up, or the opposite, when you’re really hot and you come into the air-conditioned room and you’re cooling off,” he says. “It feels good. It helps me to sleep at night and it’s just good for exercise.”