I have used an old remedy.....it has really worked for me.
Mix a stiff paste up of Brasso or other liquid metal polish and cigarette ash. Rub on the stain with small circular movements and dry off with kitchen towel. You may need to polish or re-wax afterwards, to get rid of the white bloom, but if you don't go mad with the elbow grease you should be OK.
This remedy also removes coffee cup rings - just need to find someone who still smokes. You need quite a lot of fag ash to make the paste. It really does work !
You could also try the following method, but I haven't used it so cannot vouch for its efficiency....
Apply a small amount of non-gel toothpaste to a damp, clean, lint-free cloth.
Rub toothpaste over the water spot.
Remove film with a clean, damp cloth.
Dry with a clean, dry cloth.
Polish.
B& Mrs B