LOXAHATCHEE GROVES, Fla.—On a recent Friday morning, Jessi Bartoletti arrived at the Sunsport Gardens Nudist Resort here in a T-shirt and shorts.

By evening, the 19-year-old had stripped down to a string of purple Mardi Gras beads and was dancing around a bonfire with about 200 young nudists, many of them first-timers.

"I don't think I've ever felt this free," Ms. Bartoletti yelled over pounding drums.

That's good news to the nudist resort industry, which is desperate for young nudists like Ms. Bartoletti to augment its clientele of graying baby boomers.

Membership in the two big nudist umbrella groups has been flat or declining for years, prompting a youth-recruitment effort that includes reverse-strip-poker nights, volleyball tournaments, naked 5K road races and music festivals like Nudepalooza and Nudestock.