You do not have to book these excursions through the ship - book them independently! go to
www.dolphindiscovery.com and book your swim time; then find the Atlantis sub website (maybe someone has that, I don't) and book that too. I believe it is either a $8 or $10 dollar cab ride (for the whole cab, not per person) to the park and then there is a $10 per person admission fee to the park. There is also a small beach with some pretty good snorkeling at the park, there is a sea lion show in addition to the dolphin swim and encounter, there are paths to hike through the park, some small ruins to see, restraunts and shops.