We decided to book the Amazing Secret River tour.
WHAT AN UNBELIEVABLE EXCURSION!!!
If you have the opportunity to take this excursion, do it! You will definitely love this tour. You are ferried to Playa Del Carmen on the mainland, and then transported to the site. It's a bit of a slow, rough ride to the location, due to the fact that the roads cannot be paved above the underground caverns. You'll don a short wetsuit, aqua shoes, and a cave explorer's helmet, and then set off into the caverns. Crystal clear water, unbelievable formations, and great fun! The tour has a paid photographer that takes every one's pictures along the way, since they don't allow you to bring your own camera for your safety. The packages are a little on the expensive side, but the memories are worth it.
Read gmichae's full Carnival Liberty cruise review
Carnival Cruise Line