Not exactly powered by water, but using it as a conductive agent, completing an electrical circuit powered by probably a slowly dissolving piece of zinc. Anyways, all kinds of water-powering always sound like the perfect solution for swimming pools :-) See vat19.com.
A Water-Powered clock
By rokur
rokur
Production engineer and certified swim coach. Full-time IT consultant, spare-time swimming aficionado. 2 sons, 2 daughters and a wife. President of the Faroe Islands Aquatics Federation. Likes to run :-)