I've been up and down the coast, and I haven't found a beach yet where I couldn't swim in the ocean.
My two favorite resorts I've stayed at is Dreams Tulum and Grand Oasis Riviera Maya. Keep in mind that my priorities are non-touristy and small and somewhat classy. The Grand Oasis was great and seemed deserted a lot of the time, but the drinks weren't all that great. Dreams has way better drinks, but the beach is a little rocky (though still swimmable with GREAT snorkeling). Both places you can walk out in the water and have angelfish swarm all around you.
I've heard Azul is great, but it is a little $$$.
I've stayed at the Iberostar Quetzal/Tucan a couple of times, and the beach is good, but it's way too big for me.
I hear the Iberostar Paraiso whatever is wonderful, some of our friends stayed there and loved it. Again, big and touristy.
We also stayed at Catalonia Playa Maroma this New Year's (aka The Proposal) and the beach there is not so great. And that's right next that supposedly great resort Playa Maroma, which we walked past. It looked swank, but the beach was sucky.
Does this help? I don't know exactly what you're looking for, but that's my two cents.
Good luck!