In Reply to: Lights shown by boats for night diving? posted by Frank O on September 11, 2007 at 11:03:09:

Noting that the main Coast Guard home page has a form to use in submitting questions, I posted there and got the response below. Assuming this carries the day, Andy's understanding was correct and I can forget about the extra lights.

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Note, underwater or "diving operations" in the Navigation Rules refers to the vessel being restricted (i.e. tethered) and not to --scuba-- divers over the side. This said, a vessel should display the appropriate lights and signals to indicate it's navigational status, either at anchor or engaged in diving operations (alpha flag); not both. Rule 30 or 27 would apply.

Sec. 2030. Anchored vessels and vessels aground (Rule 30)

(a) Vessels at anchor

A vessel at anchor shall exhibit where it can best be seen:
(i) in the fore part, an all-round white light or one ball; and
(ii) at or near the stern and at a lower level than the light prescribed in subparagraph (i), an all-round white light.

(b) Vessels of less than 50 meters in length; alternative light

A vessel of less than 50 meters in length may exhibit an all-round white light where it can best be seen instead of the lights prescribed in paragraph (a) of this Rule.

(e) Vessels of less than 7 meters in length when at anchor

A vessel of less than 7 meters in length, when at anchor, not in or near a narrow channel, fairway, anchorage, or where other vessels normally navigate, shall not be required to exhibit the lights or shape prescribed in paragraphs (a) and (b) of this Rule.

(g) Vessels of less than 20 meters in length while at anchor in special anchorage

A vessel of less than 20 meters in length, when at anchor in a special anchorage area designated by the Secretary, shall not be required to exhibit the anchor lights and shapes required by this Rule.

Sec. 2027. Vessels not under command or restricted in their ability to maneuver (Rule 27)

(d) Vessels engaged in dredging or underwater operations

A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shall exhibit the lights and shapes prescribed in subparagraphs (b)(i), (ii), and (iii) of this Rule and shall in addition, when an obstruction exists, exhibit:
(i) two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists;
(ii) two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass; and
(iii) when at anchor, the lights or shape prescribed by this paragraph, instead of the lights or shapes prescribed in Rule 30 for anchored vessels.

(e) Vessels engaged in diving operations

Whenever the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in paragraph (d) of this Rule, the following shall instead be exhibited:
(i) Three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white.
(ii) A rigid replica of the international Code flag ``A'' not less than 1 meter in height. Measures shall be taken to insure its all-round visibility.

(g) Vessels of less than 12 meters in length

A vessel of less than 12 meters in length, except when engaged in diving operations, is not required to exhibit the lights or shapes prescribed in this Rule.