A seaside town in France is clamping down on tourists who venture beyond the sand in their swimsuits.

“A little restraint, please!” Yannick Moreau, the mayor of Les Sables d’Olonne, pleaded on social media last week to the flocks of mostly French tourists who visit each summer.

Mr. Moreau said in an interview that the behavior had become more prevalent in recent years: Visitors leave the beach and walk into the town’s markets, grocery stores and restaurants in their bathing suits. He has seen enough.

“If you go to a market to buy local food — fruits, vegetables, meat — you cannot be half-naked with hair falling onto vegetables,” he said, adding, “It’s a matter of decency.”

In July, officials in the resort town have issued fines to 10 people — all French tourists — of up to 150 euros, or about $171. That’s the most fines handed out for the offense in July since the rule was introduced in 2020, Mr. Moreau said.

“I don’t know if it’s a reflex to show one’s muscles,” he said. “Or to tan more quickly, and not lose an hour of sunlight.”

Les Sables d’Olonne, which Mr. Moreau said was one of the first seaside resorts in France, sits on the country’s western coast and has miles of beaches. “It offers a huge space to be half-naked if you want,” he said. Or fully naked, since Sables d’Olonne has a nudist beach, too.

Many cities have put similar rules in place in recent years, as European vacation towns grapple with a surge in visitors, including scantily clad ones. In some parts of Spain, it is illegal to wear just swimwear even on seafront promenades and adjacent streets, and fines can be hundreds of euros. On Thursday, the tourism board in Málaga took to social media to remind tourists of the rules, urging them to “dress completely.”

In parts of Italy, including Sorrento, on the Amalfi Coast, tourists can be fined hundreds of euros for walking around shirtless to curb what the mayor described as “widespread indecorous behavior.” In Dubrovnik, Croatia, officials in 2018 issued a notice to tourists that they could not wander around the city in swimwear.

The rule is about respect and hygiene, Mr. Moreau said. When you’re shoulder to shoulder with others on the bus to the beach, “you do not want to be in contact with your neighbor’s skin,” he said.

Despite his frustration, Mr. Moreau was hopeful that the publicity from his campaign would help turn the town into a more popular destination for international visitors.

“Les Sables d’Olonne deserves to be better known,” he said. “Come see us, we’ll be happy to welcome you.”

If you’re wearing enough clothes.