Maybe it's something in the air—the sweetness of spring or a faint whiff of salt. Whatever it is, when boy (or man) meets girl (or woman) in balmy Myrtle Beach, S.C., it's only a matter of time before they're out on the dance floor, twirling and gliding through one of the most intimate acts permitted in public: a soft-shoe version of the jitterbug with eight basic steps and untold variations. This ritual is known as the shag, and like its home, Myrtle Beach, it is hot now and sure to get hotter.

The shag was already two decades old when it captivated Holden Caulfield, the 16-year-old hero of J.D. Salinger's 1951 novel The Catcher in the Rye. "Not a corny jitterbug, not a jump or anything," observed Caulfield in praise of the sensual rite. "Just nice and easy." The fact is, though, that the dance is not what it was and never will be again; it is constantly in the process of change. It sashayed into existence in the '30s on the South Carolina coast, where black lindy hoppers from Harlem vacationed. Slowing down the frenetic lindy, which incorporated the Charleston but emphasized wild improvisations, they added such challenging new steps as the duck walk—a foot roll from heel to toe—the boogie walk, in which the dancers' knees flop from side to side, and a lot of flat-out pelvic thrusting. Shag, not coincidentally, is British slang for fornication, and the dance soon became known as the Dirty Shag, prompting police raids around Myrtle Beach. But the shag, like Chicago, could not be shut down. In the '40s and '50s, when black music was not played on Southern radio stations, white kids flocked to Carolina beachfront bars where jukeboxes blared Blueberry Hill and Stagger Lee, ideal numbers for shagging. "It was a sexual hothouse," says Lanier Laney, 31, who helped write the upcoming movie Shag, about the summer of '63, Myrtle Beach-style. "The tension was released by dancing."

The shag was out of fashion in the late '60s through the '70s, but since 1980 visitors to South Carolina's Grand Strand, a 60-mile stretch of sand ending at Myrtle Beach, have been enthusiastically bringing it back. Today it has spread to at least 54 shag bars in such cities as Charlotte, N.C., Richmond, Va., Atlanta, Ga., and Jacksonville, Fla. The latest generation of shaggers has added challenging moves borrowed from new dances and tends to regard previous generations as fogies. "When we junior shaggers see the old shaggers enter the room," says Brian Pate, 18, "we leave and go to a movie. We shag differently—with break-dancing and moonwalks. None of the older generation would dare do that."

More subtle than the erotic entwinings of Dirty Dancing, the newest incarnation of shag has spawned both a sizzling version and tamer, jitterbug-style variations. Taking up the challenge of mastering the dance's 15 or so tricky steps, yuppies are entering shag competitions and vying for spots in an unofficial shagger's Hall of Fame alongside seasoned old-timers who haven't given up on the dance yet themselves. "I can't tell you what a thrill it was to shag with 300 friends I hadn't seen in 30 years," says Atlanta industrialist Dick "Spider" Webb, who joined 10,000 shaggers at last year's annual Society of Stranders (a synonym for shaggers) reunion. "The shag holds both the body and old friendships together."

For 25 years the seven dance floors at Fat Harold's bar in Myrtle Beach have been a mecca for shaggers. "The shag is a way of life with us," says current owner Harold Bessant, 43, whose romance with the dance has outlasted his three marriages. "I started at 12 and never stopped. Now the shag is the hottest thing going." Shag, a Dirty Dancing clone to be released in the fall, was filmed at Fat Harold's, but its cast is predominantly young. The movie stars Phoebe Cates and the supporting players include Page Hannah (Daryl's little sister), Bridget Fonda (Peter's daughter), Carrie Hamilton (Carol Burnett's daughter) and Annabeth Gish. Both the actors and choreographer Kenny Ortega, who charted the moves in Dirty Dancing, took lessons from shagging vet Barry Thigpen, 43, a Myrtle Beach real estate man, and his wife, Pat, 39. "With women's lib, there are new steps where the guy and girl are equal," says Pat. "But it remains the guy's dance because he leads. All eyes are on him."

Whether the dance picks up street moves or overtones of lib, it is fine with the traditionalists, as long as no one stops them from shining up their Bass Weejuns, pressing their Bermuda shorts and writhing around the old-fashioned way. (Shaggers, by time-honored custom, practice their moves by wrapping their hips in a dishrag, attaching it to a doorknob, and gyrating slowly.) Speed, these graybeards have learned, is not of the essence. "The shag," explains columnist Lewis Grizzard, 41, "is like doing the jitterbug on Valium." The beauty of it is, no prescription is needed.

—By Michael Small, with Linda Marx in Myrtle Beach