To further clarify, there's nothing you can charge on board (gratuities or otherwise) that will appear as a cash advance. Everything appears as a normal charge. The only distinction being made above about doing so in advance is whether or not the charge will qualify for the "6 months free interest" promotion. Also, all charges are in US$ and appear to come from Florida, regardless of where the ship is or what the itinerary is, so you don't get hit with international transaction charges.