Motorbikes that can ride on water — how cool is that? Jet-ski's and Sea-Doos or Ski-Doo's (two popular brand names for what are collectively called Personal Water Craft or PWCs) are among the fastest and most maneuverable boats of all. That's why lifeguards and marines use them. A PWC isn't like a normal boat, powered by an outboard motor and a propeller. Nor is it like a motorbike, where the gasoline engine turns the back wheel. Instead, a PWC moves along by squirting a high-powered jet of water behind it. The power of the water squirting backward pushes the PWC forward . . . . . . a GREAT and fun project to work on!