Liquib turns an image into a virtual fluid, to produce flowing, evolving transformations on a liquified surface, including water and marbled-paper type effects.  It is a graphics tool (or toy) that attempts to translate mathematics into visual imagery.  Liquib manipulations can be applied manually, or you can relax and be entertained by Automatic Effects.  The Scripting feature makes it possible to create choreographed performances of dynamic art, and performances can controlled via a connected MIDI device.  Display sequences can also be captured to Video files.

Liquib can be downloaded and used for free:

The fully functional Liquib Screensaver is also free: