Poolside in cowboy hat, heels, and nothing in between, Isolde Worsham interrupts water aerobics at the Glen Eden Sun Club, a 150-acre nudist resort in Corona, California. “All of you with new hips? Let’s modify the flutter kicks.”

The 800 members of Glen Eden plan their days around the pool. “Sags less,” one member tells me. They sun with their legs spread. They make unflinching eye contact, and avoid the cactus garden after dark. Edenites can spot “cottontails,” or new nudists (think tan lines), at a glance.