Absolutely. A couple of years ago we met two different couples on HAL who weren't going to tip. So we had a quiet little lesson/armtwisting and they figured it out. At that time the alternative restaurant was no additional charge and when we went there, we tipped at the rate of what an equivalent meal would cost at a nice restaurant on land. Obviously we overtipped cause the good news was that the server would seek us out on the ship offering us reservations even though it was technically sold out - lol.