Loose Lips Sink Ships

It's an old military saying, as you may know. I mentioned it today, along with the idiom "keep your cards close to your vest," to my class while trying to describe a character in a story who is quiet and reserved. I explained the source of the saying by saying that if a ship's location is known to an enemy, the enemy could come along and sink it, so you have to keep the ship's location a secret--loose lips sink ships.

"In that case," one of my students said, "my sister is lettin' in all kinds of water every time she open her mouth."

Yeah, I LOL'd.