I just heard a radio ad aiming to discourage cannabis use. It had a male voice talking about how he had been a good swimmer, but then threw it all away because of weed. It finished up with the line "If it wasn't for marijuana, I could have been, you know, famous or something."
Now there might be good reasons to avoid marijuana, but saying it will ruin your swimming career is a pretty poor argument. Surely even the potheads remember Michael Phelps' 14 Olympic gold medals, and also his famous bong photos?