Robert Allen

Detroit Free Press

Below the murky, rolling currents of the Detroit River is a floor loaded with centuries of artifacts: war cannons, old wooden ships, cars and hundreds of firearms, ranging from wooden muskets to automatic handguns.

Visibility is so poor that scuba divers make many of these discoveries by running their hands along the river bottom. City ordinance forbids the public from diving in the river within Detroit city limits — partly because of safety concerns, and partly because there's so much criminal evidence down there, said Sgt. Dean Rademaker with the Detroit Police Underwater Recovery Team.

"For as long as this city has been around, people have been throwing stuff into the water," he said. Detroit was founded in 1701.

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Police have recovered hundreds of guns, including 11 at one time in the span of one archway of the MacArthur bridge connecting Belle Isle to the mainland. In the police dive team headquarters, there's a mounted M1 Carbine rifle from sometime between World War II to the 1960s. On the same wall, there's a propeller from a sunken Prohibition-era rum runner found near the bridge.

Numerous cars, including a DeLorean in the 1980s, and more recently, a Jeep Cherokee and Nissan Xterra, have been removed from the water. In 2009, a police diver was searching near a Jeep, in the water not far from Alter Road on Detroit's east side, when he found a bronze statue stolen from the Grosse Pointe War Memorial. Rademaker said that if the river were ever somehow dammed above Detroit, "people would be just amazed" at the things that appear.

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Underwater visibility ranges from about 8 feet on a good day to not being able to see your hand in front of your face. At the surface, the river moves at about 5 knots (5.75 mph).

Last November, a 6,000-pound anchor from a massive, historic steamship was pulled from the Detroit River after 60 years underwater near the Ambassador Bridge. Greater Detroit was a 536-foot-long, 96-foot-wide luxury steamship with a capacity of more than 2,100 passengers that toured the Great Lakes from 1924-1950. This artifact's location was no secret, but experts believe many historically significant discoveries remain hidden in the sediment-clouded water a short distance from Detroit's shore.

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Six 1700s-era cannons have been pulled from the river from the 1980s to 2011. The most recent one was more than 6 feet long, weighed about 1,300 pounds and was found near Cobo Center.

They're likely connected to a pre-War of 1812 inventory kept by the British military, said Dan Harrison, a librarian at Henry Ford College and doctoral student at Wayne State University. He suspects three additional cannons are somewhere in the river near the same area.

"I've told them to keep looking, because we aren't necessarily done yet," he said.

The cannons would be made to fire 4-pound cannonballs — the same size as the six recovered cannons. The historic British inventory documents show 17 total cannons of this type, and 14 have been accounted for. Harrison said his theory is that the British dumped the cannons in the river because they were "too worn-out or small to do the job."

They probably hauled the cannons out onto the ice when the river was frozen over, perhaps in January or early February 1796, Harrison said. This resulted in them dropping into the river — and potentially out of enemy hands — when the ice thawed.

Farther downriver toward Amherstburg, Ontario, he said as many as seven larger cannons believed to have fallen off a barge could still be in the river.

"The artifacts that are down there are so well-preserved in fresh water that some of this stuff would be instantly recognizable," Harrison said.

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Despite invasive zebra mussels spreading to cover many of the artifacts, Rademaker said even very old items remain discernible in the water, which doesn't corrode like salty ocean water. The river ranges from about 18 to 52 feet deep, and police say the areas where they search are frequently between 20 and 35 feet deep.

The river is 28 miles long, and the Detroit shoreline comprises roughly 10 miles of it.

On the Canadian side, where Rademaker said police divers aren't allowed to operate, is even more history. Windsor Harbour Master Peter Berry said people don't regularly dive in the Canadian side, and it takes a federal permit to do so.

"I think there's a world of heritage that no one yet has discovered," he said, adding that it's especially dangerous for divers. "Very easily, you can get yourself hurt and get disoriented."

He said divers talk of a Model T with a wooden cart behind it, facing upriver, in the underwater mud near the white silos of Hiram Walker, the Canadian Club plant on the shore just south of Belle Isle's western tip.

"One could only assume that vehicle was taking liquor across, and it fell through," he said.

Divers often find plates and bottles tossed from large passenger ships that traveled the Great Lakes. In one case, Berry said a table was found with knives and forks glued to the top.

"This was the epicenter of all shipping of the Great Lakes, historically," he said. "A lot of those heritage items really, truly belong to the museums of both countries."

Contact Robert Allen: rallen@freepress.com. Follow him on Twitter @rallenMI.