The Straits of Mackinac Shipwreck Preserve is a 148-square-mile (380 km2) state preserve in and around the Straits of Mackinac. The preserve is divided in two by the Mackinac Bridge. The waters of the preserve include the waters offshore from Mackinaw City and St. Ignace, as well as all or part of the shorelines of Bois Blanc Island, Mackinac Island, Round Island, and St. Helena Island.