46 CFR §42.05-40

1. (a)This term means the Great Lakes of North America.
2. (b)As used in this part, the term solely navigating the Great Lakes includes any special service coastwise navigation performed by the vessel.
3. (c)In concurrence with related Canadian regulations, the waters of the St. Lawrence River west of a rhumb line drawn from Cap de Rosiers to West Point, Anticosti Island, and west of a line along 63° W. longitude from Anticosti Island to the north shore of the St. Lawrence River shall be considered as a part of the Great Lakes. In addition, the Victoria Bridge, Montreal, Canada, is the dividing line between fresh water and salt water in the St. Lawrence River.