I went to Cozumel last April/May. I don't have dive certification, but I went on several snorkeling tours. We just rented the boat to ourselves for a few hours and went out to Palencar and Colombia reefs. Palencar was a bit deep for snorkeling at about 50 feet, but it had a lot of current that just floated us along. I saw many, many HUGE Barracuda, but the reef was too deep to really explore. Colombia was awesome! It was about 30 feet deep and had big rock formations all over that came within 15 feet of the surface. Lots of Acropora corals and brain corals and BIG Angelfish. I can dive down about 30 feet with my snorkel so I was able to check it out well. We also went to another one I can't remember the name of. It was shallow - only 15 feet or so, but was all sand with the occasional rock here and there. We saw tons of starfish, but not much else. Clarity was terrible so I was freaked out about sharks.
As a side note, there is a submarine tour on Cozumel that was really great too. It was US$100 per person I think, but it went down to 110 feet and we saw lots of really cool reef life including Nurse Sharks, Sting rays, Angelfish, Barracuda, Lionfish, Octopus, etc. It took us to the edge of the Palencar wall so we could look down into the black abyss. I have no idea how people have the balls to dive down there!
