I got the kids' swimming pool set up again (12 foot diameter x 3 foot high straight fiber-sheet sidewall), and again, with the sun high in the sky, when I struck the side of the pool I could watch a shimmering geometric network procede from the perimeter of the pool in to the center where the network gets tighter and fainter and finally disappears from view. What am I seeing? That is, it is the disappation of the initial perturbation, the traveling pressure wavefronts, but what is going on so that I can end up seeing "lines of light" that form the network? Is this purely 1. a mechanical effect where the molecules of water are compressed together throughout the depth of the liquid into different "cells or sacless mebranes", and the more compressed molecules along the edges reflect light more (or less) -- forming the appearance of the network? 2. or is the reflection of more light coming from changes in orientation or spins at the molecular level? Also, is what I'm seeing in the shimmering network of light one view of the trail of the disappating sound wave traveling at the speed of sound in water? Any thoughts? -- Curious in Brookston Indiana.