The Refraction of Light in Water

Optical illusion (visual illusion) - error in visual perception caused by the inaccuracy or inadequacy of the processes unconscious correction of the visual image, as well as physical causes ( "flattened the Moon", "broken spoon" in a glass of water).
There is an effect of visual perception when the observer is consciously or unconsciously makes factually inaccurate explanation for the observed pattern to them.