Some examples of RAM vessels include a vessel laying, servicing or picking up a navigation aid, submarine cable, or pipeline; a dredge; a vessel engaged in surveying or underwater operations; a vessel engaged in replenishment, cargo or personnel transfer while underway; a towing vessel with a tow that severely restricts the towing vessel and her tow from deviating from their course; a vessel launching or recovering aircraft; a mine-clearing vessel.
The required lights and dayshapes for these vessels are found in Rule 27 (b-g). Rule 35 prescribes the sound signals for RAM vessels in restricted visibility. The rules are complicated, and if you operate where any of these vessels might be found you need to learn the rules. The text is available at www.navcen.uscg.gov/?pageName=navRulesContent. See also Mariner’s Guide, p. 330. Buy a plastic reference card with lights, shapes, and sound signals to keep near the helm.