system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the moon's gravitational pull have such a strong effect on the incredibly heavy and massive ocean, while it has no visible effect on a glass of water?

Or a small pond even.
gpt
The moon changes our gravity by about 16 millionths of a percent.

The pacific ocean is about 40 million feet across.  16 millionths of a percent of 40 million is about 6 feet.  This is roughly the magnitude of tides you should expect in an ocean.

Your small pond is 500 feet across.  16 millionths of a percent of 500 is 0.0008 feet, or about 25 microns.  This is about the thickness of a human hair, and is the magnitude of tides you should expect in a small pond.

Your glass is 4 inches across.  16 millionths of a percent of 4 inches is about .01 microns or about 1000 water molecules laid end-to-end.  

So the moon's gravity is moving thousands of water molecules around in your glass of water.  It's just hard for you to see it because .01 microns is smaller than the wavelength of light.