Dining table getting temporary stains with water

My dining table gets stained when it comes in contact with liquids like water. (see picture taken immediately after I put a damp platic mat). Those stains go away after few hours. (I bought the table 5-6 years back from a local non-branded furniture store for around $800 or so. This issue has been going on since then. I can't recollect if I had applied sealant over it. But, the surface has been like this since day 1 I bought). Why is this happening? Please give me some tips to fix the dining table surface so that it can withstand water and doesn't get stained.

 

I think the easiest thing would be to cover it with a tablecloth or placemats when using it. You could also get a glass (or probably plexiglass) top fitted to your table. I don't think there's anything you can do to the table itself to waterproof it.

 

The finish has been damaged. It looks like by a try or something rectangular.

Since the finish itself is damaged, replacing it is really the only option. Refinishing would be a big job for sometning that is only visible after getting the table wet. With care though the top only could be redone keeping the job a bit smaller. Still, you need to decide if the damage is worth the cure.

 

Sorry to say. but, the finish is not damaged. As I said, the table top will be back to normal in 5 hours. I mentioned this in my post "Those stains go away after few hours."
I got some good feedback on some other forum. I will follow it.

 

You can see the rectangular shape where a hot cookie sheet or casserole dish was sat directly on the table. The ghosting you see is damage to the finish. That is why the mark appears when it gets damp. It's not magic. It's damage to the finish allowing it to readily absorb water and revert to it's original milky white color. My guess is that it is a water based polyurethane though it could also be polycrylic. Both of which are easily damaged by heat.