What a terrible terrible tragedy.
I can't remember what the signs say. Is it just "No Swimming"? I grew up in New England and while I've known about the possibility of alligators for quite some time now, if I'm being perfectly honest, for the first couple of visits, I wouldn't have realised there might be alligators in the lake. "No Swimming" to me would have meant exactly that- no swimming, probably because there are weeds that could wrap round your legs and drag you under. That's what it meant where I came from, not that pottering about with the water around your ankles could put your life in mortal danger. Living in Scotland now, no swimming usually means the water gets very cold and very deep quickly, again not that you can't paddle about at the edge. I can understand why people don't understand exactly what the signs mean if they just say "No Swimming".