So I don't know what we drove through in our 2015 Corolla, but the rear bumper cover is pretty much covered with what looks like millions of water spot etch marks. There was a recent snow storm here in Colorado so perhaps it was some new deicing product. I have tried Meguiar's clay which showed a bit of brown color on the clay and claying but no improvement to the bumper seemingly confirming these are some sort of etch marks. Next, I tried some of my Meguair's Ultimate Polish which I understand is one of their least abrasive materials. This improved it a bit, but not entirely. I should note I am doing this by hand with the official Meguiars foam pads. I called Meguiars and they recommended their Ultimate Compound. I'm a bit leary to use any sort of product with the word compound in the name. Do bumper covers even have clear coat on them to make this safe? Should I give it a try? The surface feels very smooth so I don't suppose a more aggressive clay would help, right? I'm inclined to just keep using the Ultimate Polish but perhaps shift to one of these microfiber covered pads I see for sale everywhere so the product stays a bit more confined on the pad and maybe I can apply a bit more pressure. In decades of self-detailing my own cars, I can honestly say I've never seen anything like this. I would post a photo but it is really hard to capture the spots. They even sort of disappear depending on angle of view.