If skating out onto the middle of a frozen lake sounds terrifying to you, you’re not alone. Of the two terms used to describe the activity—natural skating and wild skating—“wild” seems the better descriptor. “Natural” it is not, to find oneself gliding on the surface of a large body of water. But people have been skating on ice, from ponds to canals to glacial lakes, for thousands of years. According to The Daily Telegraph, archaeological evidence suggests that sometime around 3,000 BCE Finlanders developed the first skates, made from the rib bones of elk, oxen, reindeer, and other animals, as a form of transportation during the long, frozen winters. Metal runners came from the Dutch in the fourteenth century. The first mechanically frozen ice rink? That didn’t show up until January 7, 1876, in London.

“I remember my dad saying, ‘When you’re on natural ice and it makes a big booming or thunderous cracking sound, don’t worry, that’s an expansion crack,’” Stacey Keefer says, laughing. “Meanwhile, your heart stops, and you think you’re going in.” Keefer, who is the director of the Maine Marine Trades Association, a nonprofit business support group for the marine industry in Maine, is an avid outdoor ice-skater.

Originally from Vermont, Keefer spent her childhood seeking out wild ice: the local pond, the frozen stream behind her house, and the dairy farm down the road where, in winter, the corn field would flood and freeze. When Keefer’s family moved to Cape Cod, she even found herself skating across the frozen mazes of cranberry bogs. She and her sister would don their double-blade skates, place little sandwich baggies between their socks and toes to keep them from freezing, and stay out until they could no longer feel their feet. “At one point my mom thought, ‘I’ll take her to an after-school skating program; she really likes to skate,’” says Keefer. “We got to this ice rink, and there were boys zooming around on hockey skates, and people everywhere, and I was so overwhelmed in what felt like such a tight space. I was in tears. I thought, ‘No, I like my cranberry bog.’”

These days, Keefer lives in Union with her partner, Scott Carlson, a passionate iceboat sailor. Between Keefer’s interest in skating on large frozen lochs and Carlson’s interest in sailing over them, it was only a matter of time before the two got into skate sailing with a Kitewing. Skaters holding on to these wing-shaped sails skim across the ice at speeds of 30, 40, and even 50 miles per hour. Think windsurfing without the board. There are no lines, meaning you can let go of the wing instantly if needed (a reassuring thought for a beginner), and the whole thing folds up into a little carry-on that can fit inside the trunk of a car. It’s Keefer’s new favorite activity: the constant sound of the wind as it whips over the exposed ice, the crisp brilliance of the frozen water and the surrounding snow, the ice cracking and expanding as one skates over it—an unearthly noise, deep and whale-like.

“Three years ago, when I got into sailing the Kitewings, that’s when I started to learn the most about wild ice, to study it more and to crave getting on it as quickly as I could,” Keefer explains. “I used to just bring a hockey stick and go out skating with a friend, and we’d say we’d pull each other out with it if we needed to. Now if I fall through the ice, I am ready to self-rescue. I have a plan.” To avoid falling through, the first thing a person looking to skate on wild ice should know is how to test it before going out. Ice-fishing anglers use an ice chisel (also known as a spud bar) to check the depth before using a large ice auger to drill their holes. Keefer often peeks into ice-fishing holes, but when those aren’t around she uses a hatchet, swinging the sharp side of the blade hard into the ice until she breaks through to water and can measure the thickness.

According to Bob Dill, an ice enthusiast in Burlington, Vermont (whose blog, Lake Ice, is an excellent resource), Nordic skating poles are the best testing tool for serious wild-ice skaters. The poles can penetrate down two inches with just a couple of stabs, and they are long, light, and therefore practical to carry and for checking ice depth regularly while skating along. They’re also handy for balance when transversing rough surfaces.

However you test, don’t simply test in one spot, but several, Keefer says, and continue to check as you go: the thickness can vary greatly. Also, don’t go alone. “It’s good to have someone with local knowledge,” Keefer says. “If we go to a pond or lake we’ve never been to, we’ll look at the satellite view on a map and see where the inlets and outlets are, because those are the places where the ice will be thin.” It’s counterintuitive, but the thicker ice can actually be in the middle of lakes, Keefer says.

Finally, each time Keefer goes out—whether on ice that is three inches or two feet (which can happen on Maine’s big inland lakes)—she wears ice claws on a chain around her neck for getting back on the ice if she falls through. “When deployed they look like giant thumb tacks,” Keefer says. If you do fall through, she says, stay calm but act quickly. Think about which direction you just came from, because it is the most important direction to go back to. “Apparently it was safe for a certain distance and is no longer,” Keefer explains. “If I try to exit the hole in a different direction, I may not be getting to anything better.” Deploy the ice claws with both hands and smash them into the ice while simultaneously kicking your feet. This will help to get you up onto the shelf, belly down.

Despite the thrill of danger, Keefer, who has been a sailor and a windsurfer, describes gliding over miles of wild ice with her Kitewing and her Nordic skates as more fun than anything else. She says she has always liked winter, but now she loves it and cannot wait for ice. “You feel like you’re flying,” Keefer says. “There are eagles in the sky looking at my wing, ‘Thinking, those are funny birds.’