I want to work as a meditation trainer in exchange for meals and stay on a cruise ship, where do I start looking?

Working on a cruise ship is about as different from going on a cruise as it's possible to be. Crew cabins are small, windowless, and typically shared - on some ships they are shared with more crew than there are beds, working and sleeping in shifts. Crew are not allowed in guest areas even on their time off - there are crew bars and such further down in the ship.

Working as the stress counselor and meditation teacher is going to be higher status than a dishwasher or room cleaner, but you're not going to be relaxing on the Lido deck between lessons. The good news is you get paid over and above your room and board, and you can often explore the ports of call since the guests leave the ship on those days. The bad news is you will work very hard and not get to experience the luxury of the ship.

There are many websites dedicated to recruiting kitchen and cleaning staff (as well as more specialized skills like IT and software development, entertainers etc) for cruise ships. I looked through a lot of them for a chef who was considering it. Some of the web sites appear to be ripoffs and applying to the cruise lines directly seems safer, but by reading through them it was clear that no large boat offers you the passenger experience in exchange for your labour, and never as a one-off or occasional thing. You sign a contract for 3-6 months or more, you work hard long dayss (eg 12 hours a day 6 days a week) which is just as well because there's little to do when not working, you meet people from all over the world and get to see a little bit of it, and you make decent money considering you won't be spending any of it on board.