system
Given the following post, respond as if you're commenting on Reddit:
human
Why can I lift a dry glass with no effort, but a glass 
with a wetted bottom had some suction/resistance?

I'm sure there must be some simple explanation. There's a significant difference between the two. Thanks in advance!
gpt
The bottom of the glass and the table you put it on do not create an airtight seal.  When you go to lift it, the air can easily get in under the glass and so no vacuum is created to make lifting it more difficult.

Add water, and suddenly the air trying to get in has to pass through the surface tension created by the water.  A seal is created. The pressure of the air all around the glass pushes equally in all directions, so it'll try just as hard to lift the coaster as it would to push in the water ring that made the seal.