I understand people should be clean before getting in a pool, but I don't understand what a poolside shower, a few seconds at most, is washing off? No one's washing the bits most likely to be dirty!
I'm just back from a swim session. I always do stand under the shower long enough to pook like I've been in, but more because I'm embarrassed not to than because I think there's a point. Most people don't even do that.