I don't know anything about the Cancun shops, but have done a lot of
cave diving in the area south of there, around Akumal and Tuluum. If you
are cave trained, there is alot you can do. If you are not cave trained,
there are many outfits that take OW divers on some pretty cool cavern
tours. I highly recommend a cavern tour at Dos Ojos. Ponderosa, Grand
Cenote (aka Sac Aktun) and Choc Mol are also popular cavern tour
locations. I'm sure this can be arranged from Cancun, but as I said, I'm
not familiar with doing it from there. Will you have a rental vehicle?

al

Look at www.cenotes.com

Ron Lee

I've used Scuba Cancun in the past and was happy with them.  I booked
a trip to Cozumel from Cancun with another operator a few years ago
and they subcontracted it out to Scuba Cancun.  They picked up at the
hotel, took care of the ferry tickets, and provided lunch in Playa
after the dive.

http://www.scubacancun.com.mx/default.html

I have dove the cenotes 3 or 4 times.  I have used Aqua Safari and another
dive shop that is near the pier that goes over to the Isle of Mujeres.  Aqua
Safari, you have to meet at their facility (a couple of bus stops north of
the Cancun Hilton.  The other dive shop will pick you up at your hotel.
Great dives.  Diving in or around Cancun is not worth the effort.  Reefs are
dead or dying and not much sea life. Spend the extra money and do the
Cenotes dives.

Dave