We did Castaway Sail and Barefoot Snorkel.  It was awesome!!!!  The Castaway girls are highly trained and are able to show you all kinds of marine life.  They dive down and actually pick up some of the marine life and pass it around to you and let you hold it.  You go to two separate snorkel areas, one being a shipwreck.  You will see all sorts of fish and beautiful coral!!!  Once you are done and board the catamaran, they bring out the all you can drink rum punch and beer!!!  BEWARE of the rum punch.  It goes down like water and before you know it, you can't walk : ).  The girls never let your cup go dry--they constantly are refilling it.  It has a very sneaky affect.  This excursion is very much highly recommended.