That's pretty weird...but now I have to go to the little boys room :)
That's freaky and cool :D
Witchcraft! Must be, as I have no idea how that's happening :D
Very cool camera trickery. :)
It works because the frequency of the drops is the same as the camera frame rate: if you were watching it live, it wouldn't appear to 'freeze' at 24Hz or move backward at 23Hz, you'd just see drops falling. But because the camera is shooting at 24fps, every time it samples the 24Hz wave droplets falling, there is a drop in exactly the same spot. At 23Hz, they haven't quite reached the same position yet so appear to move backward.
It's the same stroboscopic effect that makes car wheels appear to turn the wrong way on film...
Water And Sound Experiment 2: Water appears to be frozen in the form of a sine wave.