My hobby is to build the first affordable human-powered-flying-bike. Sounds crazy, yes, but if you follow the link I provided, you'll see that Nasa built two iterative models, and the team's amateur cyclist pedaled it and flew across the English channel (30 miles). Actually, I'm collaborating with two or three folks around the nation on this.

(1) Fuel Supply — Unlike carry-all jetpacks, the working mass is plentiful and you could go for hours with only the minimal trade-off of a tether-tail. The rugged off-the-shelf fire engine pumping technology embedded in the floating support boat will work as long as there's diesel or other fuel to burn.

(2) Failure Modes — F'ing up with one of those unstable, ornery, touchy wearable bombs… er, jetpacks seems like a formula for face-planting terra firma the hard way. They call it "terminal velocity" for multiple reasons. Things go wrong with the water-borne aquato jetpack and you plummet a limited number of meters and into into a relatively soft watery bath.

I agree, Brad, this is potentially as big a deal as jetskis, perhaps bigger.