If you have the time, I would suggest calling Famous Vincent and having him pick you up and head out to the reef. He charges $25 a person and actually goes out snorkelling with you and guides you through the reef pointing out everything that comes along.
It's also a nice way of getting a tour of the cliffs from the waterside.
We have used him every time we go.
Next trip we plan on heading out to Rhodes Hall for a daytrip though, heard the snorkelling was fantastic there!
