The waters of the Great Lakes on the U.S. side of the International Boundary, the territorial seas of the United States, and the internal waters of the U.S. directly connected to the Great Lakes and the territorial seas (bays, sounds, harbors, rivers, etc.) where the entrance exceeds two nautical miles between opposite shorelines, to the first point in those bodies of water where the distance between shorelines (including islands) narrows to less than two nautical miles, as measured on a nautical chart.
In the Great Lakes region, the waters within the territorial jurisdiction of the United States consisting of the Great Lakes, their connecting waters, harbors, roadsteads, and estuary-type areas such as bays, shallows, and marshes are considered coastal waters. In other areas, those waters adjacent to the shorelines, which contain a measurable quantity or percentage of sea water, including, but not limited to, sounds, bays, lagoons, bayous, ponds, and estuaries are considered coastal waters.