I've done 3 different snorkeling excursions through
DCL on Grand Cayman (I don't know the exact names

) over the past 12 years (#1 was done in the first year that DCL sailed the western Caribbean)
1. Shipwreck and Reef Snorkel - snorkeled around / over a sunken tug boat. This was RIGHT IN FRONT of where the Magic was anchored (so cool). It was like snorkeling in fish tank since the tour operators had fish food. so lots of fish and the tug boat. We then moved a little ways and snorkeled over reefs that were very active with fish and other critters
2. "Stingray City" - but ours was NOT the one where you go to the sand bar. We were in the "general area". we snorkeled in 20-30 feet deep water. If you went venturing into the reef / breakwater reef if you were not careful you could end up in less than a foot of water. But there were lots of cool sea-life and crustaceans. And we say a couple of sting rays as well.
3. Kittiwake - this ship was sunk here on purpose several years ago. It's in over 60 feet of water (it's a big ship). the top of the ship at places is less than 20 feet underwater. We where there on a fairly cloudy / stormy day but you could see the ship easily, and there was enough fish in the area to keep it interesting. We moved closer to shore for the second snorkeling stop - where we snorkel over a reef. With the overcast, the colors of the reef and of its inhabitants was pretty muted (I blame the weather

)
I would do any of these excursions again.
Have only had an underwater camera for a few years so here's a couple of pics from the Kittiwake and the nearby reef. The Kittiwake is a popular Dive location. The person you see without air tanks was part of our snorkel group. He said that it was a bit of a stretch for his lungs to make it there and back again - I would not have tried this, but I'm old.

Oh yea, you can see the dark clouds as we were boarding the catamaran. I will spread these pics over a couple of posts ....