system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:If molecules are constantly moving, why does water in a bathtub feel still?
gpt
The short answer is that molecules are too small to sense their individual movements. Bear in mind that your nerves, which sense movement, are made up of cells which themselves are comprised of uncountable molecules. If you **could** feel molecules moving, you would feel as though your whole body was constantly vibrating. Your skin would literally crawl all the time. 

The body of water as a whole may be very still, but individual molecules are still moving around and bumping into each other. The rate and ferocity at which they do this is what we perceive as heat. When the water is warmer than you, its molecules are moving with more kinetic energy than yours. When you touch it, water molecules bombarding your hand transfer some of that energy to you, and we perceive this as heat. 

So, in a sense, you can perceive the movement of molecules through your sense of hot and cold. Until it boils, hot water is just as  still as cold water, just not at the molecular level.