Believe it or not, with a steam iron, a towel, and lots of patience. You should try this in an inconspicuous place or even on an old piece of furniture first so you have the hang of it.
Set the iron on steam but not the hottest setting, put the bath towel, (I found a smaller size hand towel easier to work with), directly over the mark on the table.
If you leave the iron too long you make it worse. If you go on You-Tube and type in removing watermarks on tables to you will find lots of demo's of the process. The water stain is due to water trapped under the finish and the wood underneath. The steam heat releases it but too much heat puts more in. So patience is the key word.
Every time I clean my mirrors, they end up having tons of streaks and almost look worse than before I started. What could I use to clean them that won't leave streaks...
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https://www.hometalk.com/diy/clean/furniture/how-to-removing-wood-water-rings-mayonnaise-4294329
Removing Water-rings From Wood With Mayo!
Believe it or not, with a steam iron, a towel, and lots of patience. You should try this in an inconspicuous place or even on an old piece of furniture first so you have the hang of it.
Set the iron on steam but not the hottest setting, put the bath towel, (I found a smaller size hand towel easier to work with), directly over the mark on the table.
If you leave the iron too long you make it worse. If you go on You-Tube and type in removing watermarks on tables to you will find lots of demo's of the process. The water stain is due to water trapped under the finish and the wood underneath. The steam heat releases it but too much heat puts more in. So patience is the key word.
Otherwise refinish the whole table top.