Now I'm no scientist, but it looks like the water being force up and out of the water is creating a sort of barrier for the water coming up right behind it. And with science the way it is, the water is always trying to find the easiest way around. So if the water is going and the stream right behind it (I understand that it's constant) would require more pressure to go through it decides to veer right a bit because it's an easier path of travel. In doing so, it's causing the water behind that one to veer left a little bit to avoid the previous "gush" of water. I'm really bad at explaining things easily. I guess what I am trying to say, is that it looks like the water is constantly diverting or deflecting itself due to gravity.
Maybe I'm just totally off and should continue eating cookies and counting asterina's in my tank.