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The cold and fresh waters of lakes Michigan and Superior – free of the salt that corrodes ocean vessels – have preserved hundreds of shipwrecks.
Yet the frigid water also challenges archaeologists who require special equipment such as dry suits, heavy gloves and hoods. In the Great Lakes, underwater archaeologists usually work in water that is 40 to 60 degrees as they explore shipwrecks.
"These are underwater museums," says Keith Meverden, State Underwater Archaeologist, "and tell us about the lives of the people who worked, lived and sometimes died on the Great Lakes."
If shipwreck exploration intrigues you, the best place to begin your adventure is at Wisconsin's Great Lakes Shipwrecks. On the site, divers will find dive guides, maps, mooring locations and important safety tips. Those preferring to stay dry can watch videos of wreck dives, catch up on research and post questions to underwater explorers.
In 1987, the Wisconsin Historical Society (WHS) started studying the state's shipwrecks to create a historical inventory. Since then, WHS has surveyed, mapped and documented more than 80 sites with the help of volunteers, many of whom belong to the Wisconsin Underwater Archaeology Association and Great Lakes Shipwreck Research Foundation.
But there is more work to do. Historical records document more than 700 shipwrecks in Wisconsin territorial waters (only 150 have been located to date).
Paul Lothary, a diver and Maritime Trails volunteer, has helped with shipwreck documentation in the Apostle Islands.
"I was surprised at how intact the wrecks were," Lothary says.
Documenting a shipwreck is an intense process. Sites are found sometimes by accident and other times by using sonar or an underwater metal detector called a magnetometer.
The first survey dive may include laying a baseline along the vessel. This baseline is a reference point when mapping the site. Divers often divide a shipwreck into small sections and records the ship parts or artifacts within his or her area. Breathing air under pressure limits the amount of time divers can stay underwater. Lothary's work included operating a Diver Propulsion Vehicle, an underwater "scooter," that extends diving range.
Documenting a wreck can take days to weeks depending on the weather and underwater visibility. Sketches along with underwater video and photos, precise measurements and a site map form a more complete picture of a shipwreck. Archaeologists rarely remove artifacts from shipwrecks unless a special artifact is taken for study or a museum. Conservation requires time and expense.
"This is important work," Lothary says, "because it runs along the line of out of sight, out of mind. But these are important pieces of our heritage."
Lothary works with Tamara Thomsen, owner of Diversions Scuba in Madison. Thomsen has written numerous articles on underwater exploration and published many underwater photographs.
Thomsen has worked on the Wisconsin Maritime Trails for two years but also was a diver for the famed USS Monitor project. The Monitor National Marine Sanctuary protects the wreck of the Civil War armored turret gunboat USS Monitor, best known for its battle with the Confederate ironclad Virginia in 1862. Later that year, the gunboat was caught in a storm off the coast of Cape Hatteras, North Carolina. On December 31 it foundered and sank. Her wreck was discovered in 1974 about 220 feet deep and it was designated as our nation's first marine sanctuary in 1975.
"Many people used to go to towns and visit places like Manitowoc and Two Rivers on vacation and yet didn't know these are important places in our state's maritime history," she says. "The Wisconsin Maritime Trails work helps put it in perspective."
Challenges to preserving Great Lakes shipwrecks include looting, zebra mussels and damage from anchors. WHS works with the Department of Natural Resources to enforce shipwreck laws, but most divers are policing themselves.
Mooring buoys also have been installed by WHS at several shipwrecks to help divers find and protect the sites by allowing dive boats to tie directly to the buoys instead of dragging anchors to locate wrecks. Recreational divers may use the lines attached to the buoys for a safe descent to the wrecks.
Shipwreck divers are told to "take only pictures and leave only bubbles."
Natasha Kassulke is the associate editor of Wisconsin Natural Resources magazine.