BERLIN — It’s naked or not at all for Urs Wagner when vacationing on Germany’s Baltic Sea coast.

“It’s a really intense feeling of nature that everyone should experience,” the Berlin retiree, 57, said while sunbathing in the altogether on the dunes at Magrafenheide, Germany. “But who knows for how much longer. We’re a dying breed.”

Seventeen years after the fall of the Berlin Wall, the cultural divide between former East Germans and West Germans is being laid bare at beach resorts. Bikinis, maillots, and trunks have become the norm on as many as two-fifths of beaches previously used by nudists since Germany reunified in 1990, the DFK German Naturist Federation estimated.

Naturism was once associated with the communist East, where authorities viewed it as a normal extension of socialism and by dissenters as an expression of the freedom enjoyed by their compatriots in the West. Now adherents to the practice known as “free body culture,” abbreviated to FKK in German, blame prudish westerners for demanding that they cover up. Some people swim nude year-round.

“We may get scared away one day” by westerners, an engineer who grew up by the Baltic Sea in the city of Rostock, Ursula Kröger, 35, said. “If someone doesn’t want to do it, that’s fine. But they shouldn’t try to stop those that do.”

Since communism’s collapse in 1989, Baltic resorts have added new hotels and restaurants, renovated boardwalks, and cleaned up water pollution.

That led to a surge in western tourists, with visitors to the Baltic coast jumping to 5.06 million last year from 1.98 million in 1992, according to the statistical office for the state of Mecklenburg-Western Pomerania.

Property prices in Germany’s Baltic region rose 25% since 1995, more than the national average, according to a study by the GEWOS Institute for Urban, Regional, and Housing Research in Hamburg.

“When people with money holiday in freshly renovated resorts, the last thing they want are naked bodies on their doorstep,” the head of the International Naturist Federation, Wolfgang Weinreich, said.

As many as 12 million Germans — almost one in seven in Europe’s most populous country — visit a nudist beach at least once a year, according to Mr. Weinreich’s organization, which is based in Belgium and has 385,000 members.

Germany’s passion for public nakedness can be traced back more than a century. The first known organized club for nudists opened near the western port city of Hamburg in 1903 and gained in prominence in the 1920s.

The Nazis initially put a stop to naturism, though in July 1942, during World War II, SS chief Heinrich Himmler signed into law a regulation that allowed naked swimming if done discreetly.

After the war, naturism did not gain popularity in the capitalist West as it did in East Germany, where it took on more social significance. By the 1960s, it had become a mass movement, a historian, Hans Bergemann, who in 2000 organized a touring exhibition in Germany on the FKK movement, said.

“FKK became so popular that, in principle, no one noticed whether people were naked or dressed,” Mr. Weinreich said of people’s casual attitude toward nudists. FKK was not officially allowed in East Germany but was tolerated, head of the DFK German Naturist Federation, Kurt Fischer, said. Nudism was an expression of the desire for freedom, he said.

“In the West, going naked was a personal decision,” Mr. Fischer said. “But in the East, it was a way of life.”

So much so that the six-week-old DDR Museum in Berlin, which documents life in the former East Germany, has two displays on FKK, something that leaves many westerners scratching their heads.

“It’s a mystery to me what people find so great about FKK,” a bank clerk from western Berlin vacationing in Rostock, Anne-Katrin Bauer, 30, said. “I find it more of a disturbance.”

And that, according to easterners, is paradoxical coming from people who used to embody the idea of freedom.

Gudrun Krah, 63, donning a bathing suit under protest, said today’s mixture of nude and clothed bathers on a beach “robs it of some of the panache.”

“I just want to continue to go naked into the sunset,” Mr. Wagner said.