If they won't come off with a rag and strait cheap white vinegar, next try that same cheap white vinegar and a clay bar. If that does not work, I have had to sand really bad "Mineral" deposits with 1000/1200 grit sand paper and white vinegar, then polish with machine polisher, compound, and glaze. I would strongly suggest you not use a machine polisher unless you have a bit of experience, you could ruin the paint very quickly!
If you have someone else remove water spots with just a machine polisher, and not use vinegar and sandpaper to remove them, the spot will come back like a ghost! It will be gone when finished with the polishing, but will reappear soon after and remain permanently.