Go to Akumal and look for the dive shop, not the first one. there is a paved road that leads to a subdivison look a like. You can snorkel there and there is a restaurant i think is viva la vida. You can continue the road and look for the lagoon Yal-Ku.
Puerto Morelos is a small village that you can take a short boat ride to the reefs or 1Km swimming, this is a beautiful site you can see (early morning) Turtles eating, Sting rays two kinds sppoted and eagle ray, many softies and gorgonias. boulder size brain corals.
Many of the resorts and large turistic boats will take you to damaged parts of the reef, and I will nor recomended. You will see aquatic life but nothing compare to these two places. Depending of your time and where you are located. From puerto morelos to Akumal is about 1 hr drive, and from Playa to akumal maybe 30 minutes. Do not speed up if you are driving fron cancun towards playa or viceversa, they have police and Army checking, just be aware.
Any questions just let me know. My Brother lives in Puerto Morelos so I know the area a little bit.
Good luck and enjoy