There were structures resembling swimming pools at Auschwitz, but they were primarily water reservoirs built for fire prevention due to the lack of fire hydrants.
Auschwitz housed a large number of SS guards, and diving boards were added to one of these reservoirs for their use. Claims that these were for prisoner recreation are false.
Prisoners, particularly Jewish inmates, were strictly forbidden from using these reservoirs.
https://www.adaminsights.com/the-truth-about-the-auschwitz-swimming-pool-separating-fact-from-fiction/