system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why wet slaps hurt more?
gpt
Skin is soft, mushy, and full of lots of little cracks and holes. When you slap someone, a lot of the force from the slap gets cushioned by the skin and dissipated over the larger surface area created by those little uneven surfaces. This happens for both your hand and the slapped person.

When your skin is wet, it pulls itself taut to help keep that moisture out. This tightens it out a bit to reduce surface area and makes it slightly less mushy. In addition, the water fills in some of the cracks and holes, making the surface more uniform. This reduces the energy lost and makes the slap hurt more.

If you wait even longer while wet, like long enough for your hand to get all pruney, the opposite will happen. All of those wrinkles increase surface area and make the skin even mushier, and so the slap will hurt even less.