A childhood belief about swimming pools

When I was a kid, my mom told me that they put something special in the water at the pool, so that if you peed it would change the water around you into a different color and everyone would know what you did. I was so afraid of this happening that I always scrubbed myself off (down there) before putting my suit on because I didn't want there to be even a trace of anything on me that would alter the water color. It took me years until I found out that that's not true.