But where do they put the extra oxygen?

I saw this in Bombay. I think they're trying to sell drinking water with extra dissolved oxygen. The only reason I can think of why you might want extra dissolved oxygen in your drinking water is if the 1940's fad of swallowing goldfish came back. You never know though, I suppose.

My first reaction on seeing the poster was: "So they give me extra oxygen and I'm supposed to supply my own hydrogen? That seems dumb..."