EWOT

I was swimming with my friends in the pool, and there was a sign around the deep water area says be careful & deep water. People who put this sign up want to warn swimmer that it is dangerous to swim here if you are not good at swimming. But that increase my friends' incentives, they decided to swim over there. It is the law of unintended consequence, the rule is not to do something, but people end up with doing that thing which is not recommended.