The only invitation you need to this soiree is a big, fat full moon climbing into the night sky. Each month, on the official calendar night of the full moon, an often motley but gentle crew assembles on the sand -- with no central planning and no velvet rope. The crowd can grow as large as 500; 1000 is not unheard of. Over the course of the nighttime hours, the Beach is transformed from a tourist mecca where the self-satisfied lounge to a vibrant, feral gathering. You make your own fun here. There's no bar and no sound system. But inevitably drum circles form, people chant, and dancing erupts spontaneously. Sit in the sand and stare at the ocean. Strike up a conversation with that aging hippie or that sleek young club kid or the bewildered sales rep who stumbled up from the Loews hotel. When was the last time you returned home from a night on South Beach with sand in your shoes, a smile on your face, and money still in your wallet?