The main beach at Puerto Morelos [1] is quite pleasant; there are still some areas that are rocky or have sea grass, but it’s a big improvement over years past.
There still aren’t any beach clubs of the sort popular in Playa del Carmen and elsewhere, but it’s just as easy to stroll down the beach until you find a spot to plant your towel and umbrella.
Links:
[1] http://www.moon.com/destinations/cancun-the-yucatan/cancun-cozumel-and-the-riviera-maya/the-riviera-maya/puerto-morelos