Remember the 1996 Keanu Reeves film "Chain Reaction?" No? Well, you're not the only one. But here's the part that's relevant to what we've been discussing: the movie is about a team of researchers trying to create energy from water. (Also, Rachel Weisz is in it, and there's nothing wrong with that.)
Fans of the movie, all four of them, have long wondered: Why haven't scientists found a way to extract energy from water? The truth is, they've been working on it. In 2007, an inventor found a way to ignite salt water using radio waves. That scientist, John Kanzius, who was actually working on a technique to fight cancer, discovered that the heat from the ignited water could power a small engine [source: Stroh]. In other words, the concept has been proven that salt water is a potential power source, but development of this idea hasn't progressed very far.
At least one other scientist claimed to have developed a car that could run on water. In the mid-1990s, inventor Stanley Meyer said he created a "fuel cell" that ran on water. However, the scientific community debunked Meyer's claims, and he ended up getting sued by his investors, during which he was declared a fraud by the courts. Maybe there's someone else out there that can truly make water work as a fuel.