Puerto Aventuras This is more of a marina-beach community of boaters. But there are beaches. The Puerto Aventuras main beach is beautiful and usually not crowded. There are restaurants at the marinas and other general services available.
Akumal Akumal is a thriving little beach community of divers, boaters, fisherman and general beach lovers. There are a number of resorts and hotels in the area. The beaches here are natural but there are sandy children friendly beaches as well. This is a great place to snorkel and there are many sea turtles in the area as they nest here.
Tulum There is a fantastic beach at Tulum ruins. You can swim out and turn around and look at the ruins. The beach is crowded in the peak seasons but if you hit the main spot on the beach then go right you can find some space behind the rocks.
Further south is the Tulum main beach. This is a free-spirited beach and not the place you take grandma and the kids. You access this beach via Tulum town off of highway 307 or you take the road from Tulum ruins.