You will probably get more response if you posted this to the Cozumel subforum.
I am an avid snorkeler who has been to Cozumel. Cozumel has always been better known for its diving rather than its snorkeling because there isn't that much shallow-water nearshore habitat. Still, when I went there in 2005, there was some pretty good snorkeling off-the-beach in small areas. The visibility and coral growth was great, especially at a place called Dzul Ha beach. However, several months after I was there, Hurricane Wilma came through and devastated all the shallow-water coral environment in Cozumel. Most things less than a depth of 30 ft. were sand-blasted, and what was left was rubble. I haven't been back because of this, but from reading comments on internet forums such as Scubaboard, the scuba diving has pretty much recovered, but the shallow-water snorkeling hasn't. Friends of mine who went to Cozumel a few months ago said the snorkeling wasn't good at Dzul Ha, although the water was clear. If snorkeling will be a primary focus of your trip, I'd suggest going elsewhere. However, if you are mainly into scuba, Cozumel will still be great.
