I'm currently developing a 2D, top-down Windows Phone 7 game involving the surface of a pond. I'm trying to make the surface feel like actual water (as opposed to just a blue background with sprites drawn on top of it), and one of the effects I'm looking into is a sort of aquatic distortion effect. Basically, something similar to the first few seconds of this: http://youtu.be/1BpRsjF7QTM?t=3m17s
Any idea on how to do this in XNA? I'm sure I could figure out how to apply the answer to my particular application, but if it helps, my game involves a lot of ripples and I'd like to specifically distort the areas around and just behind the expanding sprite-based ripples.