GC is one place I recommend using the ship's snorkel op. Capt Marvin and the ships snorkel tour operator, as well as many other tour ops, go to a reef and stingray city sandbar. Unless you are there very early, the snorkel boats are lined up on the sandbar like a parking lot. However, there seem to be enough stingrays to go around, and it is a fun experience if they have never been there. Don't remember the cost difference between Capt Marvin and the ships op, but as others have said, the ship tenders in GC, and unless they are on a ship's tour or have frequent cruise traveler status on that cruise line, getting off ship in a timely manner can be problematic. Also, the time difference between local and ships time has resulted in people being left behind. If on a ship tour, the ship will wait for you. They will have to decide whether the cost difference is worth the aggravation and worry of getting off the ship in time to meet an independent op's departure and back to the ship in time for departure.