In and around Playa there are numerous opportunities for snorkeling and diving trips. You can hop on the ferry and zoom over to Cozumel for a day of beautiful reef diving or you can simply charter a panga off the main beaches in Playa and they’ll take you out to some nice dive spots.
For those interested, here is some basic information over snorkeling/dive trips you can find here.
Ferry to Cozumel: $20 USD roundtrip per person via Ultramar
3 hour trip on a boat in Cozumel to 2-3 reefs: $40 USD per person is the going rate, but you can often get these trips for $25 USD per person.
2.5 hour Panga trip from Playa: $40 USD per person, but if you have a group of 4, you can get prices down to $20 USD per person.
Laura and I have yet to make the trip to Cozumel, but we plan on spending a weekend there whenever work abates to enjoy the fine snorkeling. Maybe if I’m lucky I’ll be able to convince her to get her diver certification. Maybe.
As nice as taking a trip is, it is far more convenient for us to just hop in the sea and go explore. My assumptions were that I wouldn’t see a thing snorkeling from the beach in Playa, however, I was pleasantly surprised. Of course, there is no coral and this kind of snorkeling won’t even come close to rivaling what you will see out on the reefs; but as a little mini-excursion every few days, I find it quite enjoyable. Really, I’m always just looking for an excuse to strap on my fins 
I should mention that you should be a strong swimmer with good buoyancy control if you want to see anything snorkeling off the main beaches. You’ll need to swim 80-120 yards out to see the neat stuff and hover over large sub-surface rocks in the shallower water.
The first time I decided to try and snorkel off the beach, I had no camera. That is a mistake I won’t make again. About 100 yards off the main beach in Playa, not far from the Cozumel ferry, I swam over of an adult stingray in about 12 feet of water. I was actually really surprised; almost startled as my expectations were far lower than seeing a stingray. I’ve returned several times to this area with camera in hand and have yet to see it again.
After that, I went into exploration mode and have covered about every inch of the main beach in Playa from the shoreline out 150 yards (which is usually where any passing coast guards tell me to go back to shore) including the rocks around the ferry station and the actual ferry pier itself. For the most part you’ll just see smooth sand, but there are several sea forests of small marine plants and plenty of rock outcroppings.
Here are some of the things I’ve come across. Unfortunately the picture quality isn’t the best, but for a $12 disposable underwater camera, I can’t really complain. Getting a proper underwater camera is now on my “must do” list though!
Can you see the juvenile stingray in this picture?
Here is the stingray gliding down to the sand. Much easier to see.
I was lucky to catch this guy on camera. Haven't seen him since.
Once you are about 30 yards from the shore, you come across patches of undersea plants and rocks.
This is roughly 90 yards out to sea in about 12-15 feet of water. Looks like someone lost a tank!
Around 120 yards from the shore, the water drops down to about 18 feet deep and the sand gives way to an underwater forest. This is about as far as I ever venture out.
