Well, it's not exactly perpetual motion or energy, but it's getting closer than most such attempts. Plus, instead of being backed by some sort of random crackpot scientist, this particular project has the backing of NASA and the U.S. Navy. So, what is it? (Take a deep breath.) The Sounding Oceanographic Lagrangrian Observer Thermal Recharging (SOLO-TREC) autonomous underwater vehicle. Says Jack Jones, a JPL principal engineer and SOLO-TREC co-principal investigator:
The idea of generating hydrogen for on-demand use is certainly not a new one, as you would know if you have watched our front page the last few weeks. The benefit here is that there would not be a need to store large amounts of hydrogen on-board under high pressures. As comments on this site attest, many worry about hydrogen storage in vehicles.