My grandmother (God bless her soul) and my grandfather (not really), used to take me to the beach in the mid-70's. I used to swim underwater alot. Gram wouldn't see me for a few minutes, so she'd start to call my name and pace up and down the beach looking for me. I'd watch her, but duck under when she looked my way.
Sometimes I had her calling for over 10 minutes.
Later, I'd walk to where we'd set up, and she'd say "I was calling for you, you know", and I'd say "really? Sorry, i didn't hear"...
She fell for it every time.. she was so easy.....