Ok so we all know the Moon's gravity pulls on the ocean and makes waves, but if you look at a swimming pool its water is flat why?
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The scale upon which pools and similar sized bodies of water dwell doesn't really show the moon's gravitational influence to any relevant degree. I'm sure there may be a infinitesimally small change based on the positioning of the moon, but it's much to small to even bother with. On the larger scale, like oceans, it becomes noticeable simply because there's more water to pull on over a large, large area.