This is a very simple trip to do, most cenotes are safe and easily accessible, and although I bring my own mask and snorkel, rentals are available.
Cenote Azul is approx 120 km south of Cancun, took me about an hour from the airport.
I stayed at a small Eco-resort called Belair, that is almost directly across the street from a number of cenotes.
At first I thought some cichlids may have been melanurus, but the large cenote (Azul) was full of strictly uros, and the ones in the video may have simply been sub-dom uros and were in a small pool connected to Azul.
The large cenote had large shoals of uros, I was amazed, and got some crazy video that is too long to post, and needs editing.
I didn't try to collect, most of the visible fish were too fast and too large, I think the fry and juvies were hidden in the unaccesible tangle of mangrove roots, or in flooded forest.
Below is cenote Xpu ha, it was on the grounds of the eco-resort we stayed at.
