*sigh* I am not trying to stop the watch getting wet. That doesn't bother me. Apparently I am not being clear.
I want a screen protector for the watch to stop it getting scratched, particularly as I'd like to be able to get more for it when I sell it later. I considered just getting a small screen protector plate, but decided I'd rather have a case with integrated screen protector.
Having read the reviews for a bunch of those cases, people sometimes noted that when moisture gets between case / watch that the screen becomes somewhat unresponsive and you need to take it off and dry the inside.
So I opted to get a case that was a water seal to prevent moisture between screen protector & AW screen.
Again, just to be clear, this isn't about keeping the watch itself dry. I have no fear of it itself getting wet, well aware I can use it in the shower and go swimming with it.