We did the Pinel Island tour this past August and absolutely loved it.There is a short bus trip to the other side of the island and then a short water taxi ride. The area where they do the snorkling is quiet deep, but they give everyone flotation vests. The people that run the tour are very good and knowledgeable. They bring out bait to help bring in the fish- it was great, like swimming in an aquarium. Over where the water taxi docks is a beautiful beach. It is a sandy bottom with a gradual decline. We didnt find any drop offs. We didnt explore the rest of the island. It is a nature reserve- there was a sign explaining the island, it may have had walking paths posted. I don;t remember, we just wanted to be in the water.
I would recommend the trip and would gladly do it again.