We cruise several times a year (mostly in the Caribbean) and I always dive where I can. When in Cozumel I book through the Scuba Shack. They have smaller groups than booking on the ship and they will not take you to the same place every time. Last September when I was in Cozumel their was only 2 of us on the boat. We are doing an 8 day out of New Orleans on December 26th and a 14 day out of Tampa on February 26th.
I have booked a group before when you can get 8 cabins. You get on board credit and money back that makes the cruise cheaper. We always cruise on Carnival mostly from Galveston.
My wife does not dive but she does not mind shopping while I am diving.
We would love to find others to cruise with.