1. A vessel being used for underwater diving shall carry, in addition to the marking prescribed elsewhere in these regulations:
A rigid reproduction at least 1 m high of the “A” flag of the International Code of Signals, in a suitable position and high enough to be visible from all directions by night and day.
2. Where appropriate, such vessels may carry the marking referred to in article 3.34, paragraph 1, instead of the marking prescribed in paragraph 1 above.