It’s taken close to 20 years to find, but researchers have located a German U-boat off the coast of Nantucket. The U-550 was part of a group of German boats lurking along the U.S. coast hoping to sink merchant and military ships during World War II. A U.S. destroyer sunk the vessel close to 70 years ago, but a team led by New Jersey lawyer Joe Mazraani uncovered the wreckage on Monday. Whether the boat will be brought to the surface remains unclear. That could cost millions—an investment the researchers haven’t said they’re willing to take on.