I just got off of Voyager of the seas a few weeks ago - remember that on cruises, 18 year olds are given much more freedom! they can drink and go in the casino. One of the guys i met was 18 and liked going into the casino, and a bunch of us (some being 16) would go with him and watch him play the slots, but not play ourselves!! no one came over to us, but some crew member was watching us and gave us a few looks! be careful, you can easily hide in the casino, try to blend in! As for discos, at "the vault" on voyager, they do check IDs, however its really easy to use the ID of a sibling and also a friend! (believe it or not a friend of mine got in with another friends ID and they looked nothing alike!!)