PopSci's Adam "Easy Joke" Weiner has worked out the physics of a super crazy Japanese water jetpack. Science is cool and all, but I just like watching this guy get tossed across a lake.
Essentially, this poor bastard left the launching pad at over 200 miles an hour due to the pressure of the water built up in the pack. It looks like he's using 25 two-liter bottles that tossed him about 80 to 100 feet. Unfortunately, he didn't calculate the rate of crap entering his pants during his flight, but maybe that's a job for a physicist with less scruples. [PopSci]