Trying to simulate the light at the bottom of the swimming pool.
I treat the the noise() value of locations on the screen as their
elevation (the elevation of the water moving up and down).
The difference in elevation of a location and the surrounding locations gives the inclination of the water at that point. This inclination refracts the light of ray in certain direction, increasing the brightness at that point.
Slow. Non real-time. A shader could easily do this in real time.
