From my Galaxy review of our 6/17 sailing:
Day Ten, Nassau. A short day. Passengers cleared ashore at 8am, and due back by 12:45pm. Taxi to Paradise Island public beach access for $4 pp and $1 toll. Sandy beach, crystal clear water, few fish. Vendors provide jet skis, parasail, beverages and chairs. After 90 minutes in the hottest sun of the week, we walked to the Atlantis resort for a self-tour. We used the restrooms, viewed the shops, casino, and public areas including the aquarium where we saw sharks, stingrays, and lot of fish, all for free. Worth the trip. Taxi back to Strawmarket, which is still in temporary tent location, then walked back to ship.
The aquarium is a wall around a restaurant. There were no fees.
The "archeolgogy digs" at Atlantis had a fee, and you cannot use the beach/pool unless a guest. Anyone can use the restaurant, bars, etc.