For the first time since the Sixties, and maybe ever, there's a thriving surfing community in South Beach. On most winter mornings, up to 400 rowdy surfers litter the ocean, straddling variations of long and short boards. No, our beaches haven't suddenly developed the kind of overhead breaks enjoyed by surfers on the West Coast, or even north of Palm Beach where Atlantic swells make it to shore without being intercepted by reefs and islands. But a growing number of local wavers have discovered that from fall through the beginning of spring, when South Beach receives consistent doses of swells, barreling peaks accompany the incoming tides, big enough for carving. The best known local surfer, Ron Keindl, a former lifeguard, often helps keep order, separating "kooks" from the more experienced riders who might slam into them. "Don't go down there thinking you're going to be the man," he cautions. There are rules, he adds, and "a definite pecking order."