I just read through this entire discussion and don't have the answers to the originally posed question(s), which I think are excellent. Sure... there's some GREAT ADVICE mostly amounting to "Just be extra careful and respectful and they probably won't cite you", which has been my (successful) experience in the past, but I still want to know exactly what does "operate or be in physical control" mean, and what does "motorboat" mean in this context. Lots of good guesses, but it still seems very open to interpretation. If my boat hasn't left its mooring in two weeks, am I operating it? How about if the engine is running at the mooring to charge up the batteries while a family of 4 is in the cabin eating dinner? Which person aboard (if any) is the operator? How about if I'm operating the chartplotter or operating the windlass, but not operating the engine? It is nice, and probably pretty accurate to think that unless you're causing trouble, they probably won't bother you for it. My father-in-law was once solo sailing (while living aboard) and the coast guard pulled up alongside to do a random check of his vessel. He was not under the influence of anything, and was sailing competently and safely at the time. When they said they'd like to come aboard he pointed out (half-jokingly) how much power the Coast Guard has compared with other police and military officers since this was his house, and that the U.S. Constitution required probable cause and a warrant and protected him against unlawful search and seizure. The officer didn't find his observation amusing AT ALL, and angrily proceeded to board the boat, and did an exhaustively detailed investigation of every inch of the boat emptying every object out of every locker, looking for potential citations... and he received many... one for having a head-overboard valve that was set (and latched) to pump into a holding tank, but the latching in that position was deemed inadequate... one for his "Discharge of oil prohibited" placard being obstructed from view behind something... the list went on and on, and the fines were many, many hundreds of dollars... none of which I would consider "reasonable" attempts to keep him or anyone else safe. The vast majority of people ARE what I would consider reasonable, but there are people out there who will try to enforce rules and regulations to the exact letter, and for that reason, the exact letter needs to be very clear... even if that exact letter is that it is up to the judgement of someone... just be clear about it. Personally, my own habits are to drink nothing while underway, and even non-sailing guests drink only in moderation. Even at my mooring I doubt I've ever exceeded the legal limit... though I have occasionally had a couple beers on a hot summer evening when socializing with friends. That's with a cold engine with no key in my pocket... but it does make me wonder whether at any time I'm legally responsible for keeping myself (or all adults on board?) sober at all times... especially if "operating" is operating the fridge, or operating the chartplotter, or the alternator via the engine while docked or moored or anchored. It seems like they've just applied rules for cars to the boating world without really considering how different a sailing yacht (or other boat) is from a car. Nearly every minute in my car is moving and with the engine running and with exactly one driver. The vast majority of time on my boat is spent tied to a mooring or anchor, and with no propulsion and when it is being operated, the "operator" often changes at a moment's notice, and without stopping the vehicle.