system
Given the following post, respond as if you're commenting on Reddit:
human
Why does moisture make some surfaces more slippery and other surfaces less slippery?

For example, waterslides and smooth concrete get very slippery when wet, while very thin plastic bags are easier to open if your fingers are wet, and wet clothing is harder to remove than dry.

\*Edit: I appreciate the answers so far, but I think I gave too many examples. I'm most interested in understanding why a little bit of water on my finger tips makes it easier to open very thin plastic bags, and that hasnt been mentioned yet.
gpt
Why does water make things more slippery? Well, water molecules (or other fluids, depending on viscosity) easily move around and slide over each other. So if there is a layer of water between two solids, it can allow them to slide over each other more easily as the water molecules move around easily.

Why does water make some things more grippy? For your wet clothing example, it is because when you pull on your clothing, the water allows for a vacuum to form between the clothing and your skin. This vacuum basically pulls your clothing back on as you are trying to remove it.

Why do things like non-slip shoes work? They have patterns that channel the water away from directly underneath you to create good surface contact with the ground.