Was there a week ago (Voyager).
Dont buy from the ship!! It's a big rip off.
For about $15 you can get a taxi - will take you 10 mins to get to Atlantis.
You can walk around and see aquarium for free.
If you want a wrist band to see the Dig, use the beach, etc. - thats $26 pp.
You will not be able to use waterpark in any case - only for hotel guests.