I went on an offhsore 6 hour trip. They have a lot of companies that schedule around cruise ship times. Mine was called albatros charters and I had captain pedro. They went out of there way and busted their butts. While most charters only went a few miles around the island..our captain took us around the COMPLETE island and we fished the whole time. It's kinda pricey but well worth it.
Fished in Cozumel quite a bit but not on a cruise, although I have been on the same cruise you are taking. In cozumel, you can catch a ton of bonefish in the northern lagoon with a panga guide. The cozumel channel is great for sails but the best is spring.
Thanks for the help guys. My wife and I booked a guide trip in Cozumel, where we will fish the flats for bone and tarpon. Also the wife, and this was her idea entirely, booked a jetski fishing excursion out of Montego Bay. I'm not a fan of cruises, but the opportunity to sight cast bonefish and tarpon will ameliorate the thought of being trapped on a cruise ship.