Overheard in the Dive Shop

"Are you a certified diver or a beginner?"
"What does that mean?"
"Are you certified? Do you have your certification, your license to dive?"
"I don't know... how would I know?"
"Well... have you ever taken a diving course?"
"I don't know"
"You don't know?"
"If I had done the course, what would I have done?"
"You would have learnt how to dive"
"Oh right, then no, I haven't."