I put a wet Calphalon pot down flat on a wet synthetic countertop. None of the surfaces or liquids was hot. Bubbles started appearing a second or two later from under the rim of the pot in one area. (Video.) It looked as though air was trying to escape form under the pot and forming bubbles because of the water, perhaps as if the air pressure was greater under the pot than everywhere else. Anyone know why?
I think your intuition is basically correct. I see two possible explanations:
If the pot or the water (or both) are warmer than the air temperature, any air trapped under the pot may be heated, increasing its pressure and/or causing it to expand.
Even without heating, if you get a seal between the pot and the wet surface with some air trapped underneath, the weight of the pot increases the pressure in the trapped bubbles.