Freezing flowing water? Make water flow backwards? These [totally scientific] tricks and more are yours courtesy of Brusspup. Apparently, it is the 24 hz sine wave (that you “just” got to generate, ha) and your camera set to 24 fps to videotape this magic. The camera’s 24fps frame rate is now synced up with the rate of the vibrations of the water so the latter appears to be frozen still! Reduce the sine wave to 23 hz and suddenly, the water appears to flow backwards! Couple this scene with a Harry Potter dressed child waving his wand, and presto!
Brusspup has other magic triks on his youtube page, like the stuff that rolls “up” the inclined ramp.