A couple friends has asked me some time back if I used a circular polarizer for waterfalls. I was processing some pics over the weekend and randomly saw this 2 pics and thought it kinda showed why I used a polarizer. The left was taken unpolarized and the right was taken polarized. Both iPhone 7 plus images taken back to back with the same exact settings. It removes a bunch of reflections on the rock wall that I believe would be hard or almost impossible to remove in post processing. It usually also makes foliage slightly more vibrant but probably could achieve pretty similar in post processing if I wanted to.