I have an overhead shot of a person swimming across a pool. I then have text on top of the water, but it isn't interacting with the shot - until - the swimmer hits the text. Then I want the letters to move away as if the water and swimmer are pushing them away in a random motion. What would be the best way to start? I've experimented with grabbing one of the presets, however the ones that give me the motion I like are very complex and I can't quite figure out how to go from no movement to the random movement.