Just got back from a Coral Bay trip.
The diving was ok, but the snorkling better. The dive operator there really doesn't have a big enough business to offer serious diving, so they hit the shallower (5-10m) snorkling spots so they can cater for both divers and snorklers.
They also didn't cater very well for photography. I had to hassle them each day to ensure I got a rinse tank for my camera. They were also reluctant to give me fresh water.
The diving was good, but the vis was not. If you are interested in hard coral, then there is a ton here - over 130 species. I imagine the diving outside the reef is good when they get out there.
Anyway, the highlites were snorkling with the Manta's and the Whale sharks - awesome! Not cheap mind you, but very worth it.
I had to do a lot of cleanup on the water on this shot, as the shark was feeding on plankton (as they do).