Imagine if Leonardo da Vinci had actually built this instrument 500 years ago (when he designed it)!
Here's how it works. Here's a view from a turning wheel which demonstrates the concept. You can see the person turning the wheel at the end of the instrument in this clip. Here's an animation of the "action" (that's horsehair, not water).
Here's a news broadcast about the first crude example from 2009, and an article about Slawomir Zubrzycki's improved model.