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(a) These Rules shall apply to all vessels upon the [high seas and in all waters connected therewith navigable by seagoing vessels] [inland waters of the United States, and to vessels of the United States on the Canadian waters of the Great Lakes to the extent that there is no conflict with Canadian law].

(b) [Nothing in these Rules shall interfere with the operation of] [(i) These rules constitute] special rules made by an appropriate authority[ for roadsteads, harbors, rivers, lakes, or inland waterways connected with the high seas and navigable by seagoing vessels. Such special rules shall conform as closely as possible to these Rules.] [ within the meaning of Rule 1(b) of the International Regulations for Preventing Collisions at Sea, 1972, including annexes currently in force for the United States. (ii) All vessels complying with the construction and equipment requirements of the International Regulations are considered to be in compliance with these Rules.]

(c) Nothing in these Rules shall interfere with the operation of any special rules made by the [Government of any State] [Secretary of the Navy] with respect to special rules with respect to additional station and signal lights and shapes or whistle signals for ships of war and vessels proceeding under convoy, or [by the Secretary] with respect to additional station or signal lights or shapes for fishing vessels engaged in fishing as a fleet. These additional stations or signal lights, shapes or whistle signals shall, so far as possible, be such that they cannot be mistaken for any light, shape, or signal authorized elsewhere under these Rules. [Notice of such special rules shall be published in the Federal Register and, after the effective date specified in such notice, they shall have effect as if they were a part of these Rules.]

(d) Traffic separation schemes may be [adopted by the Organization] [established] for the purposes of these Rules. [Vessel traffic service regulations may be in effect in certain areas.]

(e) Whenever the [Government concerned shall have determined] [Secretary determines] that a vessel [or class of vessels] of special construction or purpose cannot comply fully with the provisions of any of these Rules with respect to [number, position, range or arc] [the number, position, range, or arc] of visibility of lights or shapes, as well as to the disposition and characteristics of sound-signaling appliances, [such] [the] vessel shall comply with such other provisions in regard to [number, position, range or arc] [the number, position, range, or arc] of visibility of lights or shapes, as well as to the disposition and characteristics of sound-signaling appliances, as the [Government] [Secretary] shall have determined to be the closest possible compliance with these Rules [in respect to that vessel]. [The Secretary may issue a certificate of alternative compliance for a vessel or class of vessels specifying the closest possible compliance with these Rules. The Secretary of the Navy shall make these determinations and issue certificates of alternative compliance for vessels of the Navy.]

Color note: black text applies generally; blue is International Waters; green is Inland Waters.

MyCOLREGS explanation

A surfaced submarine underway shows the same basic lights as any other power-driven vessel under Rule 23(a) - a white masthead light, a white sternlight, and red/green sidelights. But under Rule 1(c), the Navy also adds a distinctive flashing amber (yellow) identification light at the top of the sail. It isn't one of the standard numbered-Rule lights - it exists because a submarine running on the surface sits so low in the water that at night she could otherwise be mistaken for a small boat, a buoy, or drifting debris.

Summary

These rules apply based on where you are: use the international wording on the high seas and connected navigable waters, and the inland wording on U.S. inland waters (including the Great Lakes' Canadian waters, absent conflicting Canadian law). Local authorities can add special rules for harbors and waterways as long as they don't conflict with these Rules, and the government can set up or recognize traffic separation schemes. Vessels of unusual construction that can't fully comply with the lighting/sound-signal rules may get alternative-compliance certificates. On U.S. inland waters, every self-propelled vessel 12 meters or longer must carry a copy of these Rules on board.

Real World Example

Miss the demarcation line and you can be technically compliant under one set of Rules and technically at fault under the other - it's one of the first things a Coast Guard investigator or insurance adjuster checks after a collision, before anyone even discusses who did what.