1. A NOAA archeologist hovers next to the wheel of the FT Barney, sunk in Lake Huron in 1868. (Photo: Tane Casserley/NOAA)

2. The bow of the Barney. With no marine boring worms or currents to break it apart, the wreck has remained almost totally intact for a century and a half. (Photo: Tane Casserley/NOAA)

3. The port bow and anchor of the schooner Cornelia B. Windiate in Thunder Bay National Marine Sanctuary. Out of 12 NOAA-designated National Marine Sanctuaries, only Thunder Bay lies in freshwater. (Photo: Steve Sellers/NOAA)

4. Looking over the deck of the WL Wetmore in Canada’s Fathom Five National Marine Park. (Photo: Joanna Suan)

5. The bow of the Wolfe Islander II, a car ferry scuttled in Lake Ontario. (Photo: Joanna Suan)

6. Exploring a stairwell on the Islander. (Photo: Joanna Suan)

7. Navigating deeper inside the wreck. (Photo: Tom Rutledge)

8. The wreck of the City of Sheboygan, a three-masted schooner that sank during a storm in 1915. (Photo: Tom Rutledge)

9. A diver floats above the deck of a sunken ferry in Lake Ontario. With no steady currents, diving conditions in the Great Lakes depend largely on local weather. (Photo: Tom Rutledge)

10. Sitting in about 80 feet of water near the Straits of Mackinac, the Sandusky is one of the most-visited wrecks in the Great Lakes. A local scuba club recovered the ship’s original figurehead and replaced it with a replica after discovering that thieves had tried to pry it off. (Photo: Michael Schout)

11. Zebra mussels coat the railing of the Sandusky. The invasive bivalves are among the only fauna that degrade wrecks in the lakes. (Photo: Michael Schout)

12. Archeologist Paul Lothary of the Wisconsin Historical Society peeks through the deck of the Finn McCool. The wreck lies off of the Wisconsin coast in just 20 feet of water. (Photo: Wisconsin Historical Society)