Diving in a cenote is coming into another world.
It is heaven for beauty, colors and shapes. It is the hell of unexpected situations, and dangers. Cenotes are connected to the ocean, breaking the film fresh water into salt water changes your view, you can lose the orientation with all consequences, danger to your life. With cave diving you have to take the currents into account, when descending you can suddenly be dragged into another much stronger current direction. In some places organic material collects, the dissolution creates an acid bath, which you feel burn on your skin. You are in the dead zone, the decomposition produces gases, the molecules of some gases are so small that they penetrate the diving mask. This is the highest danger, the effect is the same as at great depths, you become euphoric, lose the sense of reality without help, everything is over.
Don't be scared to dive there, just inform yourself, take an experienced guide and never dive alone, follow the directions and you will have a fantastic experience. Do not dive if you are afraid. (words from my father) ventana en Cenote Tajma-Ha, at the bottom right you see the lifeline. (openen)