Seeing is believing isn't always correct. Forces that depend on rotation make scientific optical illusions, because we on earth are doing some or all of the rotating. Going back to the water down the drain. We see all around us except the water as standing still. The water in bulk, because of the sink walls, gets rotated, too, by the rotation of the earth. Gravity is pulling it down (toward gravational center of the earth). But the water isn't doing all that much rotating in a spaced fixed Cartesian axis system (where physical laws hold); it's primarily going down, otherwise it's us rotating that makes the nearly stationary water (in space fixed coordinates) look like it's doing the rotating. [I hope I got that about right]