The entrance seen from below.

Cenote Aktun Koh.
Here we go... first day, first couple of dives. Most of the underwater systems in the Mexican state of Q.Roo are fairly shallow. So dives can be made that last 2 hours... At Aktun Koh, did not go below 12 meters. I was concerned, but seems I didn't loose a lot of skills since April. Didn't gain any, either :(

Another view of the entrance:



And deep inside: