Water or Knot

Well, I'm sure there's some scientifically valid reason for this "experiment." It couldn't just be physicists fooling around, could it? Either way, it's pretty cool that they actually tied water into a knot (story and video): http://www.huffingtonpost.com/2013/03/04/knot-physics-experiment-water-knotted-vortex-loop_n_2806702.html?utm_hp_ref=mostpopular