if you mean can one just lay on a towel in the sand, then wander in, splash around & cool off, i'd say yes, there are some lovely, beaches like that - where gaz mentions, the boca del rio area up to the cut, and around caribbean villas are only some examples. the water is shallow but you can often wade out where deeper or swim off a pier. you could easily make a fun day. bring your mask & snorkel, all kinds of little critters in some places.
ex - a beach in boca del rio:
my hunny snorkling right off that same beach (taken from our balcony):