NEWRY — It’s not every day you get engaged on a water slide. But Allison Smith said “yes” Saturday in the most unlikely of places.

As Smith came to the end of the Tough Mountain Challenge course at Sunday River, she was looking forward to the water slide, one of the final obstacles of the 5-kilometer race. That’s where her boyfriend, Andrew King, had a surprise for her.

“He jumped in with me and asked me to marry him,” Smith said. “It was awesome — of course, I said yes.

“He had a plan,” she said. “But I didn’t know anything about it.”

Smith, of St. John, New Brunswick, Canada, said it was her first time at the race, now in its fourth year. She said there was little doubt she and her husband would be back next year.

The race, which drew just under 200 participants in 2010, has grown to include more than 3,000, resort spokeswoman Darcy Morse said.

Morse said the race will be back in 2014, and participants should be ready for even more obstacle upgrades. She said the resort is pleased with how well the event has grown in just four years, and organizers are especially pleased that so many racers come from Maine.

“It has a real Maine feel to it,” Morse said.

Adding to that feeling was a team from the Maine Warden Service, which has run two years in a row. The group was being filmed for an upcoming episode of North Woods Law, a Discovery Channel reality show based on the service.

And while many of the racers, including Smith and her gang of friends, come for the fun of racing, most are into staying fit. The course, covered with obstacles, is big challenge and something different than a long run or a bike ride.

Nate Berry of the Aroostook County town of Mapleton, said a group of friends has come for the past three Tough Mountain Challenges, and one of the best parts of the race is that it always changes.

“It’s a good time; they do something new every year,” Berry said.

This year, a fan favorite was the “Subterranean Dance Party,” a darkened, oversized culvert with running water and a small dance stage halfway through it. For added effect, there were disco-like strobe lights and of course, dance music.

Tania McClenents, of Ottawa, Ontario, said that was her favorite obstacle, but she had a suggestion.

“They should put a big disco ball right in it,” she said.

Of the 16 obstacles, the most challenging and confounding is the aptly dubbed “WTF” — an uphill climb under a ski lift with a small false summit. Just as racers think they are at the top, they are reminded that they are not by a sign that reads, “Just kidding.” Witty signage peppers the course. Just before the final water slide, — the one Smith got engaged on — the sign reads, “Did your training pay off?”

Berry’s friend, Dan Edgecomb, agreed the course changes made by the resort each year keep it interesting. “The small tweaks they are doing make it really good,” he said.

Edgecomb’s wife, Pam, also ran the course. She said the atmosphere that Sunday River has created around the event has made it something she wants to come back for. She said there was a sense of camaraderie among racers that’s unlike any other race event. Even the racers going for their best times are willing to lend a hand to help others over obstacles or to warn them of dangers.

“When you get around people who are doing these kinds of races,” Pam Edgecomb said, “it’s a different mentality. They work hard and they play hard.”

First-time racer Dennett Clarke of Ellsworth said running through the trees was her favorite part. Clarke was with a group of racers from CrossFit Acadia. Like others at the race, they were big on fitness.

She said the race was “my first 5K anything.”

sthistle@sunjournal.com

Race results

A complete list of race results can be found here.