Where did all the Watermelon seeds go?

We had this discussion the other day about watermelon seeds.  My kids don't believe there ever was any such thing!

How do our kids recognise this as watermelon when
they have never seen black seeds in their watermelon?

It got me wondering.  Where did they go?  How do new watermelon grow without seeds?  Are we breeding watermelon into extinction by growing them seed free?

I have so many questions, but no answers.

Anyone know anything about this?