Swarm, I just got back today and I have to say it was incredible!
Great fun, amazingly clear water and lots of friendly people.
In GC we did not dive, but swam with the stingrays and snorkel at the coral gardens. I tried to book before hand with Moby Dick Tours, but they didn't get back to me on time. I did see them at the dock, but I had already paid for the tour with another vendor. The excursion to do the same with the ship was packed with people not to mention that it was twice as expensive. So I would not recommend doing it with the ship. There were stingrays everywhere!
I have some pictures from GC
here
The was a couple who did a dive with Off The Wall Divers and another couple who booked with the ship. The first couple had a great time while the ship excursion left a lot to be desired according to them.
In Roatan I decided to book with the ship since the excursion was with Anthony's Key Resort. I knew I couldn't go wrong with them. They were excellent, nice big 48' boats and great guides.
We took a short bus ride from the port to the resort and we began to set up our gear, they asked us to check our buoyancy before we left the resort and then we were off.
We did 2 wall dives. One at a site called Harvey's Fantasy and after a nice SI at Fins & Flippers we did a site called Key Hole. We even got to see the dolphin encounter as part of our SI.
The water was about 84 and visibility was incredible even though the day was cloudy you could see over 100'. My max depth during dive one was 87' and if it wasn't because I looked at my depth gauge I would have guessed 40'. I was following a grouper that wanted to show me the sand at well over 250' according to our guide. Lots of fish life!
Dive 2 was just as good, we started so close to shore I couldn't believe the drop off. We stayed at around 50-60 feet for most of the dive, but we were in an abyss... We gently drifted along the wall for 45 minutes then went back over the reef. We did not see as much fish life on the second dive but the nooks and crannies and crevices were more interesting on this site.
They were both divemaster-lead dives, but they weren't sticklers. They briefed the sites thoroughly and let us explore at leisure while always keeping and eye on everyone. We had about 12 divers on the group and there were 2 divemasters with us. We were only limited by our air not by their time schedule which was nice since the second dive was so close to the ship. We made it back just in time for the first sitting

!
I have some pictures
here. I shot a lot more, but at that depth they just don't look good IMO so I didn't post them. This was my first attempt at underwater photography so there's lots of room for improvement.
I have to get some rest now, but I'll post some more about Belize and Cozumel tomorrow.
Wys.