Last Feb., we did a cruise with planned stops in Coz, Roatan, Belize, and Cancun. The Coz trip was my first ocean dive, and I chose to do an easy, shallow shore dive at the Chankanaab Marine Park, in leiu of dropping off a boat. I've done that dive since then, also, but I definately have learned that I prefer boat diving in Cozumel. Drift diving rocks!
We used Aqua Safari last week (during a cruise stop), and I agree that they were very professional, and presented as a good, safe dive op. We were part of a very large group from our LDS, and the group actually dove with them two days, as we ferried back from Playa Del Carmen the 2nd day. The first day, they provided us two morning, one afternoon, and one night dive. They kept our gear for us, so we didn't have to lug it back and forth. Look for our karate tournament t-shirts on the crew of Ocean II! "No Udder Place but... the Dairyland Karate Championships". LOL! For real.
And, in Roatan, we used Coconut Tree Divers, very cruiser friendly. They took us, along with other people from our cruise ship, on a two-tank afternoon dive, to work around the hours that we were in port. Friendly and professional dive op in the West End. Group with other cruisers and save on the cab fees- insist on a van- there are locals who hang around the cruise pier and arrange transportation, some of them almost got in a fight over who got to take our group. Don't pay the cab driver until after the return trip in Roatan. They will definately be there on time to pick you up. If you think it's crazy in a cab in Mexico, just wait till you ride in one in Roatan, LOL!
We didn't dive in Belize, for several reasons, but the guys we dove with in Roatan did. They took the tender in to port (these are very fast tenders, it doesn't take long at all), and they found a cheaper dive op than the ship's shore excursion, and they were very pleased with the value, and the dives. Although, they did say that the reef was in bad shape, dying or dead in many places. We planned to dive in Cancun the next day.
In hindsight, we should have gone diving in Belize, because our planned dives the next day were cancelled when the ship couldn't dock in Cancun (also have to tender in Cancun) due to rough seas. We had scheduled with Scuba Cancun (my husband has been diving with them before, they make a 1st class video), and they were very gracious and understanding when we had to stand them up. Lesson learned: dive every opportunity.
Hope some of this helps.
Foo