I saw on someone's web site an amazing image which, when you moved the mouse over it, created a drag effect like moving a stick on the surface of a pond. The entire image rippled, from the cursor outward to the edge of the image, and slowly would return to still if the mouse was off of the image. I remember looking at the source and seeing it was done with javascript, but I don't know any more than that.

Has anyone seen this or know how to do it? Or know a website where I can see an example of it? Many thanks.