You may never have thought about it, but there are a number of people working on your cruise ship who aren't members of the crew. Take the piano player in the bar, the lady who teaches a class in scrapbooking or the one who paints faces.
There's an interesting article in the Bloomington (IL) Pantagraph about one such person from their area (Clinton IL). The lady profiled was a junior high school teacher who took up face painting several years ago as a gimmick to reach her students and connect with them (we need more teachers like that), and has also been painting faces at various festivals in the area. She recently retired from teaching, and attended attended a face-painting convention in Florida. (Who knew there were such things?) There she met a representative of Sixth Star, an agency who recruits that kind of talent and provides it to cruise lines.
The idea sounded interesting to her, cruising for free and getting to take a guest, and doing something she enjoyed - painting a few dozen kids' faces a day. A few weeks later she and her daughter went on a three-day cruise, her very first, and she loved it. She now plans to cruise often for free.
If you have a talent like you see being demonstrated in the cruise lines' enrichment programs, you might want to check out the Sixth Star website and put your talent to use.