The park's manager told The Local the X-treme Faser slide was made men-only after several women complained of being hurt by water as they flung themselves down the slide, where people can reach speeds of 72 kmh.
Marcus Maier said six women had reported injuries to the genital area last year, and some of them had to be taken to hospital. No men have reported genital injuries, he said.
"These injuries are caused by the nature of the female anatomy," Maier told The Local.
But the Professional Association of Gynaecologists was sceptical. A spokeswoman said there was no medical reason why women shouldn't use such a slide - unless they were pregnant. She said she had never heard of women suffering waterslide-related vaginal injury.
Maier said few women have complained about the men-only policy.
"We are trying to do right by women; we don't want to discriminate against them," said the manager of Galaxy Rutschenparadies, which is part of the Therme Erding sauna complex near Munich.
Asked if the park had considered reworking the slide, Maier said it had never been seriously considered. The slide was new, he said, and reckoned it had cost up to €100,000 to build.
"We have some slides you can't go down unless you weigh 50 kilos - you could argue that's just as discriminating,” he said.
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Still, there appears to be a glimmer of hope for female water slide enthusiasts: The park is working on building a protective suit for women to use on the slide. "Like for ice hockey," said Maier.