When I was there, the viewing area in the river was very popular and very policed. No speedboats flying through. Idle speed for everyone and everyone was watching out for one another. If you go to kisreal's web page there are other pictures of the event that show how the river is like a parking lot. You can almost walk across it without getting your feet wet by stepping from boat to boat. It's safe.
http://kisrael.com/m/2009.07.05.pontoon.jpg