Absolutely no way would I ever submerge my phone underwater on purpose. No matter whether it said it was waterproof or not. That would be just an absolute no-no for me.
Pixel Drop, though, allows the underwater mode to work on the Pixel 9, Pixel 9 Pro, Pixel 9 Pro XL, and Pixel 9 Pro Fold with any underwater case, not just specific cases Google has vetted. This makes the feature much more accessible to people, as you don’t need an expensive diver-quality case to see those
Oh, okay. I was not aware there were specific phone cases made for using underwater, although that's still not something I would ever wish to participate in. Case or not.