[tantalor]

Yeah, but you make hydrogen fuel out of water, so you're kinda just playing accounting games with the water.

[laurencerowe]

Hydrogen is mostly made by steam reforming methane, with half the hydrogen coming from the water and half from the methane.

But then the fossil methane was made by bacteria decomposing carbohydrates and the carbohydrates were made by plants photosynthesising water and carbon dioxide.

So it all comes from water in the end, but some of it has not been water for hundreds of millions of years!