it would be cool if you could extract it from water
Electrolysis of water already exists, but will never be cheaper than steam methane reforming, even with use of nuclear power that could be used for better things.
Sure, that (((USES))) electricity.
Water vapor (the exhaust from the combustion of hydrogen) is the most potent of the greenhouse gasses.
You can extract it from water. But it is very expensive with hyrdolysis, and the energy required to do so is not practical. But yes, Hydrogen is one of the most abundant atoms on earth.