Teach 'Em Young.

"This is the sea, son. The North Sea. Never....ever....let me or your mother persuade you to go in it at any time.
When I was about your age, my dad made me go in there. I have never forgiven him. My entire body went blue within a matter of seconds and my testicles immediately shot up behind my ears. The paramedics said I was lucky to survive.
Promise me you'll never go in there, son.
I love you, son".