It's obvious enough that the normal wave pool flapper / "pump-and-dump" approach doesn't give you a tube. I always kind of intuitively thought it was wind-related, but reflecting on it that doesn't really make sense. Maybe pushing the water out with some sort of cork-screwing instead of a straight-line push? Who knows... anyway, I feel like they may stumbled onto a goldmine. Awesome indoor winter surfing, anyone?