Divers boats show the alpha flag by day.
But at night, lights are required. Only commercial dive boats are equipped to show these, but there is no recreational exemption. This is not a dive-specific light combination, but the standard "restricted ability to maneuver" (RAM) combination defined in COLREGS. It is combined with either running or anchor lights, as relevant.
Curiously, these are the same lights you should show (USCG) in some other unusual circumstances:
- Trailing a drogue.
- Hanging to a sea anchor.
- Running under bare poles in survival conditions. If you head up you may be rolled. You have little speed control.
- Laying ahull in survival conditions (not just drifting for rest--you must be restricted).
Some others are less clear:
- Hove to in severe weather. But you could probably manuver if you needed to.
- Singlehanding and napping. But there is NO COLREGS exemption for not keeping a watch.
Remotely piloted vessels also show RAM unless under close pilot control (USCG).
Without RAM lights, you are not allowed to show anything other than standard running lights. I would sure like to have something more obvious up there. The only other option is a distress light, which is not what I want.
It is not for conditions where your motions are unpredictable. "Not under command" may be more appropriate:
- No rudder and no drogue to give control.
- Powerboat with no engine.
Obviously, you could build these lights, but red all-around lights are big and expensive. Over $500, lots of amps, and heavy. Same with hoistable lights. You would think there would be some reasonable hoistable solution on the market for recreational divers, but I can't find it.