Day 4 (Rio Secreto & Akumal beach): I read about Rio Secreto on Tripadvisor and it almost immediately grabbed by attention. Just 10 min by "taxi collectivo" from Playa del Carmen, this hidden gem will blow your mind. The underground water reserve has thousands of dramatic stalactites and stalagmites. It’s like stepping back in time to witness something mysterious and truly spectacular. Before the tour began, there was an introductory video about the story behind the formations and the caves. We were then taken into a van and driven for about 20 minutes deep into the woods. They gave all the gear required, suit, floats, water boots, the works.