Long time readers might remember when I covered jetpacks way back in August 2007. Also you might remember from that post that the jetpack, or rocket belt as it was originally known, hasn't really progressed much since it first flew (more like a 30 second hop) in 1961. It turns out that designing a flying machine compact enough and light enough to be worn as a backpack is a non-trivial - nay, near intractable - problem. Clearly lateral thinking is required, and that is exactly what the designers of the Jetlev Flyer employed to produce a water-powered jetpack.
Instead of carrying a severely limited amount of propellant (means of propulsion) on your back, the Jetlev Flyer designers ingeniously tethered their jetpack to a water-skimming service module - think small Jet Ski-sized craft. With a nearly unlimited supply of high pressure water pumped up to the light-weight jetpack from the service module below, the jetpack can stay aloft (maximum altitude 30 feet) for what will seem like an eternity compared to untethered designs.
I know it isn't a fully autonomous jetpack, but I admire the ingenuity and the lateral thinking on display in the design of this water-powered jetpack to offer an alternative to what seems like an intractable problem.
Thanks to New Scientist for shining a light on this story.