Moving a hand in a bathtub produces surface waves, most of which dissipate.

“And so there must be some things that are stable, and it turns out, under some conditions, error-correcting patterns emerge. For instance, you sit in a bathtub, you move your hand, and you see that all sorts of waves emerge on the surface of the bathtub when you do this, and these, um, uh, waves are propagating over the surface of the water, and most of them just dissipate.”