Having stayed for 2 months in cancun and pdc, we were able to snorkle a few different areas. For anyone whos interested, I thought I'd share my favs and least fav spots. In playa del carmen I snorkeled a few times on the northern part of the town area where there is reef. Its not great but there is enough there to make it worth the swim out. The swim out to the reef takes only 5 minutes. It is shallow water snorkeling. Pumaal just south of pdc is also worth seeing. Its very shallow snorkeling. Not great snorkeling, but ok. Akumal was another place which is known for its snorkeling and for good reason. It is a great place to snorkel. Lots of reef to see and an easy swim out to it. This is also shallow snorkeling. There is also a place called half moon bay in the akumal area. Its more shallow with decent snorkeling. Also there is the park there where you can pay entrance to snorkel. Its only $6 entrance, but you can easily go in on your own without entering their park and paying entrance. The park area has decent snorkeling with a slightly different feel with some funny nooks and crannies to snorkel over. Lots of tame fish. I prefer the main Akumal beach area for snorkeling over all the other close by places. Tulum snorkeling was a tough go. The reef is a long way out to swim to get there. I did make the swim out but once I got there I found the current and waves to be very strong by the reef area and hard to snorkel. So this area I wouldnt choose to try snorkeling on your own from the shore. Isla mujeres does quite a few snorkeling tours in an area right in front of town. I did get to try it while on a booze cruise. If you're a beginning snorkeler its ok, but I'd rate it as not so great. Not really much of anything to see there. The only other area I've snorkeled in isla mujeres was at garrafon park. I thought that snorkeling was also not very good. Puerto Morelos was one of my fav places to snorkel. The reef is quite a ways out though. It took me around 20 minutes to swim out to it. Very few people swim out, as most people pay to go on the tours out to the reef. They are very strict about making people wear the life jackets around the reef, and they must be the big orange jackets and not the inflatable green ones. I got chased back in twice for not having the proper jacket on. The swim out to the reef is through water around 20 feet deep but is a fun swim since you can see conch and starfish on the swim out. Also lots and lots of baracuda there. Finally cancun snorkeling, south end behind club med. Before it got covered with sand it looked like it survived Wilma ok. I did get out to snorkel the deep side of the reef where the water drops off to 50 feet. I dont know what it looks like after the beach project has thrown so much sand its way. The shallow water part of the reef doesnt look so good anmore. The jungle tours have new markers placed all over around a section of the reef on the southern end of club med. Personally I think that area isnt very good for snorkeling and especially with them limiting how close you can get to the reef. The boat ride out is fun, but the snorkeling part of the tour isnt so great.