Cozumel is good for drift diving, but the last I heard the reef was destroyed by a huricane last year. On the other hand, be sure to go to Stingray City when youre in Grand Cayman. The snorkeling at Stingray City is often referred to as "best snorkeling experience in the world." Actually you are not even snorkeling. You will be about a half mile from land, but you will only be standing in knee to waste deep water. Then the Stingrays will be all around you like great big puppy dogs. Even if somebody could not swim or was afraid of the water, they would still love Stingray City. In Grand Cayman I remember seeing the cruise ships anchor off shore and then ferrying the passengers in small boats. In Key West and Cozumel they have Docks.