I'm looking to dive a cenote (particularly something that will give me a taste of cavern diving) near Playa del Carmen and get some reef diving in somewhere as well. I heard you can take a quick ferry out to Cozumel but I was wondering if it's worth it to make the journey out there or if i should stay near Playa del Carmen and dive the reefs there?
I was also told it'd be good to get my advanced open water cert before diving a cenote, what's the consensus on that?
It's not a "quick" ferry to Cozumel to dive. It's doable, but it'd be a long day, with several arrangements in place (transport to ferry terminal, ferry to Cozumel, transport to dive op, boat dive out. Get picked up and finish at a different place (it's drift dive, to different places). Then transport to ferry terminal... Cozumel drift/reef diving is very good, worth staying a few days.
Cenote diving is quite different than other dives. When arranging, do tell the DM you are a new OW diver. They often take a few people out on dives and if most of them are very experienced and go to more difficult dives, it won't be suitable for you to join those groups. Once you begin the dives and go some ways, it's not easy to cut short to take someone back.
Some people may not realize they react different in dark confined places. Some feel claustrophobic in small space and feel uncomfortable or even panic. If you are fine, that's good.
A few people mentioned the need for buoyancy control, more than having AOW. That's quite true. It's not open space above and below, and without good buoyancy control, one can float up to hit/touch the wall/rock about, or sink down to hit/touch rock below.
The water won't be cold, a 3mm long wetsuit is often good. The instructor/guide I went with for a few days, wore 7mm long, because he was often guiding more than 2 dives in the day. Cenote diving can be fun, but be prepared it's quite different.