Pretty sure day passes are $140/person. I don't see the price on the Atlantis web site, but they do mention the passes:
Atlantis, Paradise Island has opened a limited number of day passes for visitors to Paradise Island until further notice.
Day passes are available for purchase at the Discover Atlantis desk in Coral Towers and space is limited.
Individuals under 18 years old must be accompanied by an Adult 18 years or older.
ETA: I just found this info on another site:
Atlantis Day Pass 2015 Prices
Atlantis has not changed pricing on its 2015 day pass pricing as of today, January 6th. Here are the quoted rates from Atlantis: “Access to the Aquaventure Waterpark and marine habitats at Atlantis are FREE for guests staying at the resort. Passes may be purchased by day visitors on property, but availability is limited – and may be closed – during periods of high resort occupancy. Passes are $125.00 on all dates except for the following, on which they are $149.00: June 13 – August 15th, November 21st – 30th, and December 20th – 31st. Children (aged 4-12) tickets are $80.”
Atlantis Day Pass 2014 Prices
Here are details from the Atlantis on 2014 Pricing “Access to the Aquaventure Waterpark and marine habitats at Atlantis are FREE for guests staying at the resort. Passes may be purchased by day visitors on property, but availability is limited – and may be closed – during periods of high resort occupancy. Passes are $125.00 on all dates except for the following, on which they are $149.00: June 13 – August 15th, November 21st – 30th, and December 20th – 31st. Children (aged 4-12) tickets are $80.”
Money Saving Tip: For families or larger groups looking to purchase Atlantis Paradise Island day passes, consider reserving a hotel room at the
Beach Tower of the Atlantis or the
Comfort Suites. The Beach Tower is the lowest priced hotel on the Atlantis property. The Comfort Suites includes day passes and is next to the Atlantis property. A one night stay is usually less than the cost of day passes for a family of four. Not only will you save money by doing this, you will also have a room where you can shower if you want. Be sure to confirm with the Comfort Suites that they are still giving day passes to their hotel guests prior to booking. When booking both hotels make sure you factor in the full price of the room including taxes and fees when deciding to use this option over buying day passes out right.
http://www.allaboutparadiseisland.com/how-to-get-an-atlantis-day-pass/