I’ve talked to someone who was big on enviro issues, and hydrogen. He told me that water would be a big source of hydrogen. Since water is H2O, I was told, all you have to do is run water through a machine to get hydrogen.
I’m sure it’s a bit more complicated than that. But to people like him, water is going to save the environment as we transition to hydrogen fuel cells.
That ‘machine’ is electrolysis...around 40 percent efficient.
Large quantities if hydrogen are more efficiently derived from chemical reactions of compounds other than water...but still in no way feasible as a large scale fuel.
Oh...one more thing. The ‘fuel cell’ is a catalyst, composed of semi-precious metals. Completely impractical.