It depends on what you want to do at the resort. You can purchase tickets directly from the hotel for $25 to view the aquarium and take "The Dig" tour. The "Atlantis Beach Breaks" that are offered by the cruise lines allow you to use the beach (a designated area is assigned to cruisers), and usually provide a lunch, BUT you can only walk around the pool area - you can not use the pools, water slides, lazy river, etc. A wrist band is required that is only issued to guests of Atlantis or Comfort Suites. If you wish to use all the facilities, my suggestion would be to book a room at the Comfort Suites for the day ahead of time. They have full resort privileges and - depending on how many people are traveling together, can actualy be much cheaper than the cruise excursion.