oh man you just reminded me that I was somehow only a couple months ago introduced to the concept of water caustics (the wavy reflect-y stuff that appears on walls near pools of water) and so this time around I've now gone down a very lovely rabbit hole of understanding how they are rendered in computer graphics (and rendered in real-life optics of course): https://www.chaosgroup.com/blog/what-are-caustics-and-how-to-render-them-the-right-way