Here is my summary of my trip. I just returned Sunday. I ended up diving with Abyss Dive Center in Playa Del Carmen. I got a referral from someone I trust who lived there and knew the Canadian owner of this shop. We did 6 dives in 5 different cenotes over 3 days. They have a max of 4 divers. We were lucky so it was just my husband and I all three days. Our guide was Rodrigo. He was excellent. We dove Chikin Ha, Taj Mahal, El Pit, Dos Ojos and Dreamgate (2 dives). All of the cenotes were great but I think my favorites were Taj Mahal and the bat cave in Dos Ojos. Dos Ojos is very popular. Many shops do two dives there but one was enough for us. First of all do the bat cave side as that is really cool. Our guide got us most of the way through the other side as well on the same dive. I would not want to do two dives in this cenote as the second half was just not that great. Chikin Ha was very nice as well. El Pit is deep and was worth checking out but if you've been in the blue hole it is about the same. Dreamgate is a private cenote that our guide chose well. I don't think many shops go there. I saw a few large groups at the popular spots so I would choose a small group operator. Good buoyancy is a must. Photography is tricky as you need a lot of strobe and a wide angle lens. Three days of cenotes were good but were also enough. I can check that off my list. Worth it definitely but not for more than 3 days. I would recommend Abyss but the only down side is that you have to meet them at a meeting place on the beach. They will pick up your gear and will take care of it the entire time you are with them but they can't pick you up (at least not at the Hyatt) as the hotel would not allow them to. We did get dropped off at the hotel, however. If diving the Cenotes stay in Playa Del Carmen or south of there. Akumal looked nice as did Talum but I was happy we were in Playa. We rented a car which I also recommend. The car was only $52 for the week but be advised that you must pay $18 per day for liability insurance regardless of whatever credit card you have or insurance policy you purchase. Your card will cover the car but they require that you have the liability insurance in case you strike a person. Taxis are not cheap there so we found it very worth it. Be aware that booking sites for cars will not inform you about the $18/day. I don't want you to be surprised. The last day of cenote diving we followed our guide down and afterward went on to Coba ruins, Talum, and checked out Akumal. It made sense since we were south anyway.
We wanted to try snorkeling with the whale sharks who are in season near Cancun now so I will share my experience with that. After spending four nights in Playa Del Carmen we drove up to Cancun and stayed at the JW Marriott. All the whale shark operators are up on the north end of Cancun so staying there saved getting up extra early to be transported up there from Playa (which is common). The owner of Abyss Dive Center made all our arrangements. We were picked up from our hotel and driven to a spot were a lot of operators leave from. I never really knew who the company was we were with but they had several boats. The driver of the van said it was Underwater Editions but their website does not work. I don't think it mattered, however, as the prices are all pretty much the same and the boats all look about the same. Speaking of BOATS, there were at least 50 circling around these poor whale sharks. The ride out to the sharks was VERY rough. I am used to rough seas but this was pretty bad and was worse on the way back. There were 12 people on our boat (should not go with any more than that). 5 were puking the entire trip. After 1 1/2 hours we saw what one person thought was an island and my husband thought was a marina. Nope. It was a mass of boats all circling the whale sharks with anxious snorkelers ready to jump in. Only 2 snorkelers can go at a time with a guide so you take turns. Fortunately we got a few turns because the sick people only went once. Yes, it is SPECTACULAR to see these beautiful creatures and we were close. Many times I was right above them or directly in front or next to them. It is a wonderful experience to see these beautiful animals that close. I do have a concern though about how safe this whole thing really is, particularly for the sharks. Several we saw looked like they were most likely struck by props. There are so many boats maneuvering around to pick up and drop off snorkelers it would not surprise me if there are accidents with the sharks or snorkelers. I'm not saying it is not a safe activity I'm just saying that I think the Mexican government should think about regulating the number of boats that are out there. When I say 50 boats I am not exaggerating. I stopped counting at 50. A few tips: wear sunscreen despite the supposed rule against it. Most products are biodegradable today. The burn you can get out there for all those hours can be brutal. Drinking water - the boat supplied it but be aware there is no toilet for the entire time (approximately 6 hours) so we didn't drink it. That, of course, is not a good idea. We stopped at Isla Mujeres on the way back so we were able to walk to shore and get a beer and use the bathroom. Make sure you check the weather as far as the swells. The ride back was even more rough than the way over. The boat would occasionally hit a wave and would slam down so hard it actually shot up my spine to my head. Both of our backs are still sore 3 days later so make sure you are in good enough shape and for goodness sake take sea sick medicine even if you don't think you need it and take it before you go. I have had back surgery and even though I am fully recovered and in good shape I did not enjoy the back pounding we took all the way back (about 1 1/2 hours to the island).
If you have never seen a whale shark then this may be worth it (normally $189-$199) but if you have seen them diving and/or are not in optimal shape you may wish to skip it. Hope this helps.