Captain Cake:
I literally do this at least once a year! There's a cruise company called MSC that I use from the south of the UK and their food has always been amazing, I look forward to the evening meal every day. The ship I always go on has an all day world cuisine buffet, and also waited breakfast, lunch and dinner and there's no limit to what you can have. Along with unlimited drinks and cocktails I always come back from a 1/2 week cruise absolutely ballooned!
In fact, I always look forward to getting home because it's the time of the year where I can actively measure that I've gained the most rapidly in the shortest time.
Nofbar:
How much do you gain on these cruises?
This depends on a lot of things. Without a feeder for encouragement or support, over two weeks its usually around 7lbs for me. But that's always been with family or friends who wanted to do activities and didn't want to indulge the whole time.
With support and a goal, I think that number could be a decent amount higher.