Quintana Roo, Mexico
Although its name suggests it is only one big cenote, in reality there are two interconnected cenotes. You can swim through a tunnel from one pool to another. There is an open lagoon part and a cave section. They are connected by wooden walkways.
Gran cenote is suitable for both snorkelling and diving. When I visited with my friends Elena and James in 2015, we saw a group of divers going very deep. They told us that the depth is 10 metres (in the cavern zone) and the cavern tour lasts 40 minutes. But the water is so clear that if you just put your face in, you will see a different underwater world: stalagmites, stalactites, columns... Bring a flashlight if you can to see more of the darker spots of the cave.
When you snorkel, not only you see the world under the water but the jungle and the sky are also reflected in the water above and around you; it is true magic. The water is like a mirror from both sides. The outside world seemed reflected in the crystal clear waters when I snorkelled.
Overall, it is actually a small cenote (despite its name). The main cenote has a central platform with lockers and two ladders going down into the water. The water here is dark. A rope with buoys leads you into the deeper waters and you can use it to rest. On one side, there are turtles, and to avoid disturbing them, you can't swim there. Just sit and watch them for a while; they are charming. Like in all cenotes, there are also small fish around. Sailfin mollies and catfish are harmless and fun to watch.
If you swim through a small tunnel, you will get to the second cenote, which is rather shallow. It is fun watching the water changing its colour and temperature. The cave is full of bats but they won't harm you. Just enjoy the nature around you.
The shallow pool has soft white sand and is suitable for children, which makes this cenote family-friendly. You can get out and walk around the cenote.
There are lockers available (which are not common to all cenotes). The property also offers decent bathrooms and changing facilities (this is also not common to all cenotes). We brought our own floating 'noodles' but you might try going without (or rent a life vest).
The garden is also well maintained. It is a great place for a picnic (if you bring it with you, although there is a small shop on the property for snacks). As for the price, back in 2015 we paid 60 pesos but I am sure the price doubled by 2017.
How to get there:
To get there, drive from Tulum towards Cobá until you see the Gran Cenote sign on your right (on km 4). This cenote is popular so avoid weekends if you want to avoid crowds.
Mix & Match:
The best is to come here after visiting Tulum Ruins (Ruins) unless you are hitting Tulum beach. Alterntively you can visit here after the Cobá ruins if you are not visiting Cobá cenotes.