Sue,
I'm a bit late to this but here's my 2psi. I'd been to Playa area diving twice before I tried the cenotes, primarily after reading about how people here on the board were so enamored with them (TSandM being one of them!). Not having any real idea what they were like I had visions of what I had seen/read about cave diving - having to take off your gear and cram it through a small hole, 7' hoses, trying to squish myself through tight spaces, having to be very careful about not stirring up the bottom and silting out the place. But once I had read more and checked out pictures and videos I got in touch with my dive guy in Playa - Jason @ fantaseadive.com (playacountryboy here on the board) and booked Coz, Playa and cenotes. I went with Luis from Playa Scuba (Jason uses them for cenote guides) the first time to Dos Ojos and had a BLAST!
Water is wonderfully clear and although there are some smaller areas I never felt squeezed. Good (great) buoyancy is VERY important and will improve your experience immensely, but once in the water I never once thought - holy crap, how will I get out of here - I just marveled at the beauty. Luis was a great guide and we did the barbie line and the bat cave. Pictures here (mixed with some other dive pics from the trip) -
Diving pictures by byteme45 - Photobucket
I was hooked, so our next trip down last June we booked pretty much the save dive setup w/ Jason - Coz, Playa and Cenotes, this time Klaus took us (again w/ Playa Scuba) and we went to Grand Cenote and Temple of Doom. My wife and a friend don't dive so they spend the day at Grand Cenote swimming and snorkeling. They had a BLAST while we drove back to Temple of Doom and dove that. Very cool experience diving through the halocline - much different than Dos Ojos. Grand Cenote was great as well, quite a bit shorter dive than any of the other three but possibly the most beautiful. More pictures and a video -
Cenotes pictures by byteme45 - Photobucket
Temple of Doom and Grand Cenote dives on Vimeo
I'm a huge fan of them now and while there is obviously some risk the reward is well worth it. There is no way I see myself ever being the guy who is swimming through muck and taking gear off to fit through a hole barely big enough for me to fit through, doing cave cert, etc. However, when I started diving I was convinced I'd be a warm, clear, blue, salt water, vacation diver only. HA! I have since purchased a drysuit and routinely dive inland lakes in WI and Lake Michigan where I've been as cold as 39F and 5' vis. So, who knows - but as for the cenotes, if you watch a couple videos and get a bit of a rush, or sweaty palms, go for it. If you feel like you need to run out of your office gasping for breath...skip it!
Great advice from whoever said get in the ocean for a couple dives first to shake the rust off and get your buoyancy down. Weighting will be different because cenotes are primarily fresh water but I'm booking a cenote dive every time we're down there now. I love them! And make sure you stop on the way down and back for awesome tacos - very inexpensive and super yummy!