Leisure pools (Freizeitbad) are common in Germany. Offering water slides and fun pools they make a great family activity. Many also have sauna and spa areas (most sauna areas will be fabric free.)
You could well be familiar with the H2O pool in Herford, Aqua Mondo Centre Parcs or the Bad Lippspringe Therme.
Below is a list of three other Frietzbad options you might not know so well. Make sure to check the Corona rules and booking conditions at each pool before you go.