I had a few on my deck lid and used 3M.....took em right out then gave it a good coat of wax.
I should state that the 3M Imperial Hand Glaze worked in my case as the spots were not on the R for long.
They do say to carry a bottle mixed up with a solution of 1/2 distilled water and 1/2 distilled white vinegar in a spray bottle and carry it in your vehicle along with a soft, clean cloth. When you notice water spots, move the vehicle into the shade, let the surface cool down, spray the paint with this water/vinegar solution and wipe it off with the soft, clean cloth. The spots should come right off. Your waxed surface may be dulled by this solution, so apply a coat of wax when you get the chance.
To avoid them.....dry your vehicle as often as you can even after a rain storm if possible.
3M Perfect-It ll Rubbing Compound Fine Cut removes fine scratches, oxidation, coarse swirl marks and water spots!