The Kinsey Institute at Indiana University estimates that as many as 4 million Americans participate in some form of group sex or couple swapping. Susan downs the last of her pink drink and moves ever closer to the young blond. The young couple sits down on a leather couch. But one night three months ago, he suddenly died. Soon enough, though, they're invited to join a group of regulars — two men and three women — seated at a table. He always declines, though. Says Monte, as he prepares for a busy weekend night that will include dozens of couples: After a day of fun, the couple heads for the door, and the woman goes back to the hot tub. Neither man says a word. She has her arm around her partner, but she turns and flashes her chest to the group before walking out the door. Almost immediately, similar clubs started opening in Boston, in Chicago, in Los Angeles. With its welcoming beaches, year-round sunshine, and fine appreciation for vices, South Florida has become the mecca of swinging in this country. Other screens show porn. Every employee must embody a delicate blend of attentiveness and discretion. She explains that she came of age in the '70s and always had a bit of a wild streak.