When Trevor and Hayley Gilmartin set out to renovate their Michigan home, they had no idea their project would turn into an unexpected dive into the past—quite literally. What began as a simple plan to remove a non-functional indoor jacuzzi ended with the discovery of a hidden room 20 feet beneath their house, shrouded in mystery and a bit of eerie history.

The Gilmartins purchased their home on River Road in 2020, fully aware it needed work. The house, which had been repurposed from an old water pumping station, came with plenty of quirks. But nothing could have prepared them for what they uncovered in March 2024 during their renovation.

"We always suspected there was something under the indoor hot tub in our home," Trevor told The Times Herald, explaining the mystery they’d been pondering for a while. The hot tub, which didn’t function properly, was the first thing they decided to tackle in their renovation project.

A Mysterious Discovery

After removing the jacuzzi, the couple found a "manhole-like thing" beneath it, as Hayley described to Newsweek. This wasn’t part of the original design—or at least, not anything they expected in a living room. "I think anyone finding a manhole under their house in pitch darkness is going to find it spooky," Hayley admitted. What they found was an underground room filled with water, stretching 20 feet down into the earth.

“We did some testing to make sure the water was OK to get in,” Trevor explained to CBS Detroit. As experienced scuba divers, they had the right equipment to explore the mysterious space, with Trevor leading the descent.

Exploring the Hidden Room

Trevor’s curiosity led him to explore the room. "Getting in was like, every inch was OK; I can do this, you know. Nothing's bit me yet," he recalled with humor during the dive. The room, which he estimated to be about 30 feet long and 20 feet wide, held cold, clear water. "I tried pumping the water out, but after eight hours, the water level was unchanged," Trevor noted, describing the difficulty of fully draining the space.

The couple shared their discovery on TikTok, where their video quickly went viral, amassing over 30 million views. The mysterious nature of the find captivated viewers, with many speculating on what the underground space might have been used for.

Unraveling the Past

The Gilmartins began researching their property’s history, hoping to find answers. They discovered that their house had once served as a water pumping station in the 1940s, constructed by the Dow Magnesium Plant. "We live on Lake Huron and found that the room is connected to the lake through a six-foot pipe," Hayley shared with Newsweek, adding that the water seemed to come directly from the nearby body of water.

Some locals speculated that the room might have been used for smuggling alcohol during Prohibition, given its proximity to the St. Clair River. “We were told by people in the area that our house used to load brine onto freighters during World War II, but we’re not sure how accurate that is,” Hayley said. She added, “The wildest theory we’ve heard is that it was used in Prohibition days to smuggle alcohol over from Canada since it’s so close. Although we do find many Prohibition-era bottles in our area.”

The Future of the Tunnel

For now, the couple is focused on exploring the room further. A wooden barricade still stands at the far end of the room, and Trevor has been working to remove it to see what lies beyond. "It's slow work though, as the water is cold and hard to see in, and the wooden wall has proven surprisingly sturdy," Trevor told The Times Herald.

In the meantime, they’re brainstorming ways to use the extra space. “We’ve thought about everything from turning it into a game room to installing a bowling alley,” Hayley joked. The couple has also considered putting another hot tub in the space, continuing the quirky history of their house.

What’s Next?

As the Gilmartins continue to explore and research their home’s hidden history, they’re eager to learn more. The couple is still deciding what to do with the underground room and hasn’t ruled out further exploration. "We want to find some way to prevent water from pouring in," Trevor said, explaining their desire to turn the space into something useful.

Whether the underground room was used for smuggling, as part of wartime production, or something else entirely, the couple’s discovery has sparked the imagination of millions online. For Trevor and Hayley, the adventure is far from over.

If you have any information about the history of the Gilmartins' home, they can be reached at [email protected].

Watch the video here:

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