MINNEAPOLIS (WCCO) — On a frigid winter day, Mark Manthey dreams of diving.

“The shipwrecks, always the shipwrecks,” Manthey said.

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Not in the Caribbean’s warmth, but the cold abyss of the Great Lakes.

“These wrecks have a story to tell and through diving, we’re able to research these stories and tell the stories of these wrecks,” Manthey said.

Ken Merryman and Jerry Eliason have been hunting shipwrecks since the 70s. In the Great Lakes, there’s no shortage.

“Estimates are around 8,000,” Merryman said.

They’ve searched for a German U-boat sunk off Newfoundland in World War II. And last summer found two wrecks, the Manasoo and J.H. Jones, a day apart.

“And it always bugs the heck out of us when somebody knows where a wreck is that we don’t know,” Eliason said.

“Sometimes we don’t know if we were the first,” Merryman said.

Aboard the “Hey Boy,” they’ll search an area based on archival records and best guesses, burning time and gas as they go.

“We refer to it as mowing the lawn because basically, you’re just going back and forth in a predetermined area,” Eliason said.

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Sonar acts as their underwater eyes. By towing a tethered transducer called a “fish,” the return signal sees what they can’t.

“It’s rare that you see it the first time and it’s, ‘Oh yeah, it’s a shipwreck,” Merryman said.

Manasoo was lost in 1928, along with 16 of the 21 people aboard. Images from a drop camera confirmed their find, and software then stitches together incredible 3D images.

“I don’t know that I’ve ever had a dive that was all of, ‘Holy mackerel, look at that. Look at that,'” Merryman said.

Inside the Manasoo, Merryman saw the wood pilot house, a bicycle, even a 1927 Chevrolet – incredibly intact and preserved in the cold waters.

And rarely do they find human remains. Still, it doesn’t minimize the reverence.

“They’re grave sites – very definitely,” Merryman said.

For Ken and Jerry, each find closes the final chapter of a tragic maritime history and gives answers to the families of those lost.

“We go down and work with an archeologist to document the sites and put them on the national registry of historic places,” Merryman said.

It’s a careful balance of adventure and ethics. Solving mysteries of the deep, one shipwreck at a time.

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Ken and Jerry will be back at it come summer and plan on hunting wrecks in Lake Michigan.