I have to say that I have now done the dive excursions on the RCL cruises 4 times. I have no complaints. One cruise line sponsored dive in Nassau, we ended up with diving with Stuarts Cove. My son and I were the only people on the dive excursion and the only people on the 46' Newton dive boat. We had an incredible escorted dive by the dive master. I consider myself an experienced diver and have dove all over the east coast, Florida, Bahamas and Carribean. This was an awsome dive experience. I was very glad booked the dive excursion through the ship as their policy is not to leave anyone who is late getting back to the ship who is out on one of their sponsored excursions. Stuarts Cove is a fair distance from the port and our cab was almost out of gas and had to divert to find a gas station. We were 30 minutes late getting back to the ship. I hate to think what would have happened if we had gone off on our own.
I used the ships dive excursions in Cozumel, Grand Cayman, Jamaica, St. Thomas, St. Martin, Belieze and Costa Maya. I have never had a bad experience with a dive booked through the ship. The only one thing I could say that I thought just slightly bothersome, no big deal really, was the fact that the cruise lines restricts dives booked through them to 80ft max depth.
Anyway, there is my two cents worth. Have a great time on your trip.