Windell Oskay of Evil Mad Scientist is making a remote-controlled boat that uses magnet as a propulsion device.
Rember the silent caterpillar drive from the movie The Hunt for Red October? The caterpillar drive was a fictional magnetohydrodynamic propulsion system. Magnetohydrodynamic (MHD) propulsion is a means of using electrical current, instead of a noisy propeller, to push a ship through the water.
Surprisingly enough, a working example of this futuristic drive system is quite easy to build. Assuming that you've got the materials handy, you can build one in about a minute. You'll need a strong magnet, two pieces of thick copper wire, a little dish of warm water, salt and pepper, and a regular battery.
If you think it's all science fiction, Mitsubishi built a MHD-powered boat called the Yamato in 1992 | Magnetohydrodynamic Drive [wiki]