Since I recently did a brief class/talk on telescopes, I was poking around looking for examples of astronomical seeing. Here are a couple of videos I found that serve the purpose. In both, you can pretty clearly see the “underwater” effect of seeing.
http://www.youtube.com/watch?v=2kEXMCQw6VY
http://www.youtube.com/watch?v=5vytMN7RBlE