If you are looking for a 1/2 day or full day beach away from the large resorts and crowds you might consider Paamul. Located south of Playa del Carmen and north of Puerto Aventuras it can be reached by taxi, collectivo or bus - but the last two options would leave you out on the highway and it is a bit of a hike , maybe 10 minute walk. There are a few restaurants, went to one of the originals, Arrecifes de Paamul  for lunch- is about $30 USD for food , beers and soda for 6 . It's kind of off the beaten path - you may find only 8 or 10 other people on the beach even during spring break! The shore is full of shells and broken coral, so water entry can be a little tough without water shoes or flippers. Good snorkling can be found towards the southern end of the beach.

Pa'amul is a very unusual place.  A Mexican land owner had as a grant from the government been given some beach front.  He decided to make it available for people with rec. vehicles and campers to go during winter.  He'd rent/lease spots right on the bay, and over the years, the expats and sun worshipers came.

It has become so popular, that now the rule is:  you can pull a trailer onto a site that you buy (or lease), and after establishing the camper as main living area, you can add to it!  Make a front porch.  An outside kitchen attached to the trailer.  Build a second story and have a rooftop!  Many folks help the Mexican carpenters build it "palapa style" with very inexpensive pole-beam construction and palm thatched roofs!  It is a way of owning a little piece of Mexico on the beach (and a very nice beach with a reef!).  You are snuggled next to each other, but the prices are truly low! 

Now they've built a little motel and swimming pool adjacent to the mini-residences.  All the members of the community of Pa'amul can use it!  They place is very civic minded.  They have lots of social and sports activities IF one wants to participate.  And, if a hurricane is bearing dead-on at Pa'amul, many folks just leave their home-made additions, pull the RV out  and drive it inland to safe haven.  If the hurricane has knocked down, blown away your palapa roof?, for cheap you just rebuild!  Who needs hurricane insurance if the place you are insuring is.... disposable!