No, seriously, shower before entering the pool

Here's one of those moments where I feel like an idiot. You know those "Shower before you enter the pool" signs? Apparently, that rule is meant to prevent the spread of bacteria, like Cryptosporidium, and is, thus, somewhat rather important. All this time, I thought it was about keeping hair product out of the pool. The more you know, etc. (Thanks, Sara Aase!)