The Jetlev-Flyer is a tethered jet pack that uses water instead of rocket fuel. The pressurized water is pumped up a hose attached to a custom Jet-Ski. From Popular Science:
It took four prototypes and more than 200 flight tests to get it right. But now, with a mere 30-pound pack, the Jetlev-Flyer is almost ready for production, generating 430 pounds of thrust and letting (Raymond) Li fly forward at 22 mph up to three stories high. His next unit will get up to 35 mph. Want one? Late this year, the craft will go on sale–just be ready to dish out close to 130 grand."A Water-Powered Jetpack"