My Wife: "Grandpa had to clean the pool last week because it was full of algae."
Me: "Do you think he was scared of the sharks in the pool?"
Lucy (7): "No!"
My Wife: "Maybe he was scared of the jelly fish."
Me: "Why not?"
Lucy: "Because swimming pools have chlorine and sea animals don't like chlorine."
Well, fine if you want to get technical. :-p