Hidden Worlds Cenotes offers an excellent opportunity to snorkel or dive in  caverns that are part of a vast network that makes up a single underground river system. The water is crystalline (and cold), and the rock formations impressive. These caverns were filmed for the IMAX production Journey Into Amazing Caves. The main form of transportation is “jungle mobile,” with a guide tossing out information and lore about the jungle plant life you see. You’ll be walking some, so take shoes or sandals. If you’ve toured caverns before, floating through gives you an entirely different perspective. The owners have also installed a 180m (590-ft.) zip line on the property, a zip line roller-coaster-style ride called Avatar, and a Skycycle that has you riding a recumbent bike over the treetops. They now offer full-day packages that include several activities. Transportation from Tulum, Akumal, and Puerto Aventuras is included in admission fees.