Coastwise refers to a route not more than 20 nautical miles offshore on any of the following waters:
(1) Any ocean.
(2) The Gulf of Mexico.
(3) The Caribbean Sea.
(4) The Gulf of Alaska.
(5) The Bering Sea.
(6) Such other, similar waters as may be designated by the District Commander.
46 CFR § 125.160
Each term defined elsewhere in this chapter for a particular class of vessel applies to this subchapter unless a different definition is given in this section. As used by this subchapter