33 CFR §175.105

1. (a)Visual distress signal means a device that is approved by the Commandant under 46 CFR part 160 or certified by the manufacturer under 46 CFR parts 160 and 161.
2. (b)Coastal waters means:
   1. (1)The U.S. waters of the Great Lakes (Lake Erie, Huron, Michigan, Ontario, and Superior);
   2. (2)The territorial seas of the United States; and
   3. (3)Those waters directly connected to the Great Lakes and territorial seas (i.e., bays, sounds, harbors, rivers, inlets, etc.) where any entrance exceeds 2 nautical miles between opposite shorelines to the first point where the largest distance between shorelines narrows to 2 miles, as shown on the current edition of the appropriate National Ocean Service chart used for navigation. Shorelines of islands or points of land present within a waterway are considered when determining the distance between opposite shorelines.