Water and electronics does not strike me as a perfect combination, but the artist Antoin Fourneau and Digitalarti Artlab has made a LED panel where the LEDs light up when water is sprayed on the panel. Read more about it at the thecreatorsproject blog in their blog entry "Water Light Graffiti Lets Users Create LED Art With A Water Gun" (The video is posted on Vimeo by Digitalarti.)