I haven't used the Megs product yet but the
Chemical Guys Water Spot Remover has worked well for me thus far. It works best on light to medium etchings. The other option is you can polish the surface as others suggested. I generally start with a light polish and use more aggressive ones as needed. Starting with a light polish like
Meguiar's Ultra Finishing Polish M205 or the
Menzerna PO106FA Nano Polish (Super Finish) works great. It's certainly possible you'll need a more aggressive polish afterward like the
Meguiar's Ultra-Cut Compound M105 or
Menzerna Super Intensive Polish PO83. These polishes generally can remove 95% of the water marks I have encountered. If this doesn't work let us know and we can come up with a plan at that time. If you have any questions please let me know.