When swimmers shower away impurities (and focus on the perianal area) they help reduce the risk of waterborne illnesses, such as diarrhea, swimmer's ear and skin infections. Fecal matter, in particular, contains germs that may be ingested when swimmers swallow contaminated water.
every public pool asks you to shower before you swim.
they wouldnt have to put up the sign if they followed the rules already posted id assume