I'm a sucker for mysteries, and a huge underwater maze sounds like one. There are over 3000 cenotes at Yucatán area and many of them connected to another by underwater tunnels. For Ancient Mayas some cenotes were the only source for sweet water so ritual offerings were made to placate the Rain God. Sometimes even people were sacrificed.
Cenote Zacil-Há was the most beautiful of the cenotes we visited. It was small and clear watered, connected to another cenote nearby. While we were swimming, 6 divers started their dive from the other cenote towards us. We could watch the bubbles come up from our end of the tunnel. Wish I had the nerve and experience to go dive there, but cave diving isn't exactly the most safe hobby in the world - especially if you're a bit claustrofobic.
Tulum ruins & animal friends taken over it
The food & drink
Few things to try if you ever decide to explore Tulum.
Fresh coconut water served from actual coconut. If you're up for a local way to drink beer: michelada. It's basically beer with lime juice, spices and sauces. You either love it or hate it. I loved it. You could skip lunch and have just this.
Seafood, especially ceviche. It's raw fish or other seafood cured in lime juice and spices. But make sure you eat in in a good local restaurant, not at a tourist place, there's a huge difference in taste. We ordered ceviche from our hotel - horrible. Then again from local seafood restaurant - amazing. And when lobster season, you can eat it pretty much everywhere.
Seafood restaurant to visit.
La Barracuda was really good. The picture below shows their portion size when ordered for 4 persons. HUGE!