Surface tension propels tiny boat without sails or moving parts Answered
From the New Scientist:
WATCHING Sung Kwon Cho's model boat glide silently across the still water with no propellers or sails, you'd be forgiven for thinking a phantom hand was drawing the vessel forward. The boat is actually being driven by water surface tension, the same force that allows some insects to skate across the surface of a pond.
The design is inspired by Pyrrhalta beetle larvae, which also use surface tension to propel themselves. Since it requires no moving parts, the method should be more robust than those involving propellers and may use just a hundredth of the power.
Another story on the NetworkWorld site (with a few skeptical comments.)
Doesn't look too difficult to replicate, does it?