What a cenote actually is
The Yucatán Peninsula has no surface rivers because rainwater filters immediately through the porous limestone rock, forming an underground river system that around Tulum ranks among the most extensive in the world, with hundreds of kilometres of interconnected flooded galleries. A cenote is, essentially, a point where the limestone ceiling collapsed and exposed that underground river, creating a natural pool of cold, extremely clear freshwater.
Different cenotes, different experiences
Some cenotes, like Gran Cenote, are open and shallow, ideal for swimming and snorkelling among small fish and tree roots hanging from the surface. Others, like Dos Ojos, combine partly enclosed caverns with stalactite formations visible from the water, explorable by snorkel or certified diving for those wanting to venture into the tunnels. Semi-open cenotes, with a central opening letting light in, produce the shafts of sunlight cutting through the water seen in most photos of the area.
How to visit them properly
Most cenotes charge an entrance fee and some require showering before entering, with no sunscreen or repellent, to avoid contaminating the ecosystem; it's worth wearing your swimsuit already and bringing your own towel. Going early morning, before large groups arrive from Tulum or Playa del Carmen, makes a noticeable difference both in how quiet the place feels and the water clarity for photos. For those wanting to dive into the deeper caverns, it's mandatory to go with a certified cave-diving guide, a different specialty from open-water diving.