I just came back from Coz and there were a bunch of people on my dive that were from the Cruise ship. The company was Aquaworld and they ran a nice efficient operation but were not very personal. We dove santa rosa reef and paradise wall.
I was very concerned at first because the boat was very large and was packed but 1/3 was for snorkeling, 1/3 was for a submarine and the last third was for the dive. There were 3 groups of five divers and the dive master was very safety minded and knew where to find the interesting critters. We saw a nurse shark, turtle, very large grouper (4-5 ft) green and black spotted morays , lobster (just the antennae in my case). All in all not a bad dive but not as cozy as some of the ones I have done before. They were also very helpful in swapping out there gauges for my dive computer!
Good luck and have fun