If you're a U.S. citizen forget about getting a job on the cruise lines. I'm a U.S. merchant sailor and I work on government chartered vessels that pay pretty well. Almost all cruise lines are owned overseas and they primarily hire 3rd world crews and pay them squat in very poor living conditions (you won't be living like the passengers). If you're really interested in looking into this as a career check out
http://www.seafarers.org/. This is the largest union for American merchant seamen and has entry level jobs. If you're really interested you could go to my alma mater and become a merchant marine officer
http://www.usmma.edu/. There is one U.S. owned cruise line that is operated by U.S. crews and officers but it's in Hawaii. From what I've heard, they don't pay nearly as well as most of the other industry. As far as working on gaming vessels, that's another story. I worked on a casino boat in Indiana and didn't like it. However, stuff like that is a lot more like a "normal" job as you go home every night. PM me if you want some more info.