Tulum Beach is one of the most beatiful places in mexico. Tulum's beaches are just north of the Sian Kaan biosphere reserve beaches. Without question, some of the biggest powder beaches on the coast are in Tulum. Tulum beach is a nice small beach right in the famous Tulum ruins, but the best are just south, along the road to Boca Paila. 
That's the same road that goes to the Sian Kaan Biosphere and Punta
Allen (at the bitter end). To get there take the Coba road east (sign
for Boca Paila) and then bear right on the coastal road (south). There is also great beach the other way (north, toward the ruins). Beach access is generally through the cabana resorts you will be passing. If you like beaches, it just doesn't get much better than this!
A word to the wise... if you go, The Tulum ruins are some of the most
frequently visited archaeological sites in Mexico, and a number of new
hotels have sprung up in recent years to cater to the increase in
tourism. Most hotels are located along a strip of
beach coined the Hotel Zone. Visitors can choose among typical hotel
accommodations and smaller, cabana-style hotels or campsites. One of Tulum's most unique and impressive lodgings is Azulik Villas, 15 private villas constructed of rich, local hardwoods and featuring carved tree-trunk bathtubs, in-room massages, aromatherapy and waterfront views.