How to control light with water

as a network engineer: I think you missed one of the most intriguing features of fiber optics. it can carry different wavelengths of light (we call them channels) . sticking with your laser pointer analogy: it's possible to send the light of differently colored laser pointers through the water at the same time and sending a different morse code on each - color only is a difference in wavelength/frequency after all. if I got your attention you can take a look at the Wikipedia page covering this topic: https://en.wikipedia.org/wiki/Wavelength-division_multiplexing there's even more science in there but the page is pretty OK