Car that runs on water

"Honey, we are building a new concept car at the University"
- "yeah?"
"Yeah....a car that runs on WATER!!"
- "Wow, isn't that great?"
"Yes, the idea is that the car will use water since that is so abundant".
- "Well, I will give you a car that runs on water. It is called a 'STEAM ENGINE'."
"Huh?"
- "Why do you guys want to reinvent the wheel??"
.
[Pause]
.
"Well, do you know how a steam engine runs?"
- "On steam"
"And how do you make the steam?"
(My DH is on professor-mode now)
"Do you know what the first law of thermodynamics says? It says....blah...blah...."
- zzzz.....zzzzz.....zzzzzz
"Oh Boy!!"
- zzzz.....zzzzz.....zzzzzz