We just played it on the Wonder. In our game, it was similar to the game Scattegories. Each round, we'd be given a letter of the alphabet, and then be asked to name things in different categories. "A fruit that starts with A," "a boy's name that starts with A", etc. After each round, the lady MCing revealed what SHE had chosen. If your answer matched hers, you got an extra point. The trick was to figure out what she was most likely to choose/write down, but it was also just kinda... guessing.
Perhaps they play the game differently on different cruises, but that's how it went down on the Wonder last week.