Speaking of forward-thinking resort towns, Playa del Carmen corrects nearly every mistake of Cancún's Zona Hotelera. Pedestrian-oriented Fifth Ave ('La Quinta' – where it's wise to keep an eye on your belongings after hours) is one block from the water and lined with bars, nightclubs, take-away tacos and tacky souvenirs. Keep walking north to remote beaches where the crystal-clear water is home to some of the world's better snorkeling (even better if you daytrip by boat to nearby Cozumel Island). Also consider renting a car and go cenote-hopping for a surreal dip in rain-filled limestone sinkholes.