You already have nice answers and comments, just let me point out that you probably have already seen this effect at work: sometimes very [fast-moving wheels seem to move in reverse][1]. 

The flow in the fountain is not reversed, the droplets are falling. However, if you create a "periodic" system of droplets (in fact there are several droplets that are almost equally spaced), you can use the illusion given by the " [wagon wheel effect][1] ". After all, the periodic system of droplets is just a "unrolled cycle" and the effect is due to a "sampling error of a periodic signal" (every time the stroboscope light switches on your eyes take a "snapshot" of the droplet's actual configuration).

[Here][2] you can play with a periodic signal and see what happens when you modify the sampling rate.

Note: also the neon lamps have a discharge frequency of ~50 Hz, so they can create a stroboscope effect, thus, any machinery rotating at multiples of this frequency may appear to not be turning. This can create safety problems in factories.


  [1]: https://www.youtube.com/watch?v=BFeUb1mnKyQ&ab_channel=ChanceYoung
  [2]: https://jackschaedler.github.io/circles-sines-signals/sampling4.html