PORTLAND – While a snowmobile may make a poor boat, two men who encountered open water while racing across Maine’s second-largest lake managed to ride their machines across the icy water to save themselves, wardens said Monday.

The episode unfolded when three riders zooming across the frozen lake encountered a wide swath of open water over the weekend.

One of the riders was missing and presumed drowned after his snowmobile sank Saturday night, but the other two riders made it to safety, said Mark Latti, spokesman for the Maine Department of Inland Fisheries and Wildlife.

The story that the survivors told shocked game wardens.

The distance one of them traveled was 21/2 to three miles, said Sgt. Tim Spahr, the investigating game warden. “It’s staggering when you look at it – how far this guy went on a snowmobile over open water,” he said.

While snowmobiles aren’t designed for water, it’s widely known that they’re capable of riding across the water’s surface for short distances, a practice known among riders as “skimming” or “skipping.” The trick, riders say, is to maintain speed so that the belt that drives the snowmobile becomes something of a paddle wheel.

But it’s an extremely dangerous practice. Make a wrong move or let off the throttle, and the snowmobile will sink like a rock. After all, modern, high-powered machines are not lightweights. Some of them weigh close to 500 pounds.

“In theory, it does work. But it’s certainly not a situation that anyone wants to find themselves in,” Bob Meyers, executive director of the Maine Snowmobile Association, said Monday from his office in Augusta.

Skimming was outlawed by the Legislature in 2003, but the practice continues on lakes and ponds across the country.

Videos of snowmobiles scooting across open water are posted on YouTube and other Internet sites. In some states, there are competitions in the summer, when the water is not dangerously cold, to see who can skim the farthest.

Wardens say the three men from Maine and Massachusetts who were riding Saturday night on Sebago Lake didn’t intend to ride on open water.

The two survivors told wardens that they were zooming at 40 mph to 60 mph along a trail across the frozen surface of the lake, which is a 20-mile drive from Portland, when they were surprised to run out of ice and hit open water.

At that point, they did the only thing they could do: They gunned the throttle for a white-knuckled ride across the water, Spahr said.

Jonathan Herbster of Bedford, Mass., traveled up to a mile and came ashore at Sebago Lake State Park, Spahr said. Gary Huntley of Oxford kept on chugging across the dark lake until he reached safety three miles later, Spahr said.

After their harrowing rides, the two men could find no sign of the third snowmobiler, Paul Blanco of Carlisle, Mass., Spahr said.

Divers found his snowmobile in 30 feet of water Sunday, and divers continued to search the lake Monday for his body.

Huntley and Herbster couldn’t be reached for comment Monday.

Spahr said the men had no choice but to try to skim to safety, but the warden reiterated that it’s a dangerous, and illegal, practice.

“The instant you let off the throttle, you’re sunk – you’re done,” Spahr said. “Every concentration is keeping that snowmobile straight and fast. If you have a cramp in your hand, and you let off the gas, then you’re sunk.”