We all know how light bends slightly as it passes through water. Remember that school experiment where a pencil placed in a glass of water appeared bent? It was nothing but the refraction phenomenon at work.
The refraction property of water is a very intriguing phenomenon that can bring loads of fun. Try moving a glass of water in front of a pattern of black and white squares. See how they are transformed into rectangles?
The refracted light distorts the patterns and makes it appear as something entirely different and weird. See the video below as the diagonals and other patterns are changed into something completely different: