An experiment in bio-mimicry and alternative power sources.
Alex Villanueva and a team of researchers primarily from Virginia Tech University are developing Robojelly, a biomimetic robotic jellyfish. It is intended as a self-propelled surveillance vehicle. It is modeled as closely as possible on the appearance and propulsion method of a moon jellyfish.
Perhaps most excitingly, it does not require batteries or any external power, because it is powered by the hydrogen naturally present in seawater. If you want all the information (and I do mean all) you can read the paper published in The Journal of Smart Materials and Structures, Volume 21, Number 4 online (free for 30 days after publication).