That is some really solid advice. Mine is less so, but what the heck.
Usually on cruises there is a formal night where everyone dresses up and often photographs are taken etc. This is the perfect night for a proposal (in my humble opinion). In fact, if it can be accommodated, I would have a photo taken with a chair or bench and pop the question right in front of the camera. Maybe the photographer can even get the look on her face as you propose.
Congratulation and good luck!