This is a traditional Czech summer swimming spot ("koupaliště"). The pool is a concrete basin with filtered, famously cold water.
Right next to the water, you'll find the "Krčma na koupáku", a pub that's a major part of the experience. According to reviews and their online menu, they serve a variety of pizzas, fried cheese, langoš, and schnitzel at very reasonable prices. [1] You can also get draft beer like Litovel Moravan and Josef. [1]
It's a laid-back place perfect for a hot day when you just want to cool off and have a simple, affordable meal.
There is a symbolic entrance fee to the swimming pool area.