But that was not enough for some of those who objected to the nudists. A pastor led protests in the beach parking lot. Republicans lawmakers tried banning nudity on state-owned land, but the effort fizzled.

Although it is a misdemeanor in Wisconsin to “publicly and indecently” expose one’s genitals, a succession of state and county officials have taken the position that mere nudity is not enough to warrant prosecution at Mazo Beach unless there is some other disorderly or lascivious conduct involved.

This year was not the first time the state closed some of the woods near the beach to separate the lewd from the simply nude; in 2007, it made 13 acres off limits. Now, with problems persisting, it has added two part-time deputy wardens and increase patrols at the beach after a rise in arrest numbers last summer suggested that the problems might be getting worse.

Citing a heavy workload and a small staff, Mr. Plautz said Mazo Beach was patrolled just 32 times from 2007 to 2011. Even so, last year alone, the agency arrested 42 people for drugs and sexual activity in just nine days of patrolling the area, up from 15 arrests during six days in 2010. There have been at least six citations so far this year.

Even as clothing-optional resorts and cruises gain popularity, it has gotten harder to find nude beaches on public land in the United States over the past 20 years, with some people being given tickets for nudity in places like New Jersey, California, Florida and Hawaii. In such cases, lewd behavior is often cited, said Bob Morton, the Texas-based executive director of the Naturists Action Committee, the legal arm of the Naturists Society. “That is the excuse that authorities have used, whether it’s real or not,” he said.

While the state has made no imminent threat to shut down Mazo Beach, some of its visitors worry about what would be lost if it ever did close. On a recent Friday, parents with children and middle-aged skinny-dippers extolled the freedom and nostalgia of sunbathing nude, the exhilaration of connecting with nature au naturel.

Claudette Richards, 58, who has been coming to Mazo Beach for nearly all her life, said it was a place where she had found body acceptance, including after she had a mastectomy. “It’s a place to be who I am,” she said, sitting in the sand, the scars from her surgery exposed to the open air.