Nuclear fusion is all to easy. A certain type of field has to be generated into the reactor core.This field breaks the h2o into hydrogen and oxygen and when the two ignite it changes back into water again etc.
This same field is used in systems on the international space station to breakdown water vapor in the air produced by people breathing back into oxygen and hydrogen. At present the oxygen is recycled back into the system and the hydrogen is being dumped overboard.
so many things wrong about that assertion.
1 ) the space station and the space shuttle use Fuel Cells, not any "certain type of field"
2 ) what you are erroneously describing is not Fusion. thats a chemical reaction.
3 ) "igniting things" is what we call a chemical reaction, specifically. "fire" it's sorta new. you probably havent heard of it yet. but it does NOT make "water"
4 ) if that were fusion then fusion was perfected 50,000 years ago in a cave near Olduvai Gorge in Kenya by a Homo Habilis who still hadnt figured out how to make stone tools.
5 ) not even close. thats not even how fuel cells work. heres a pretty picture:
~
http://americanhistory.si.edu/fuelcells/basics.htm