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I was discussing this on the last trip and I had presumed it was from centrifugal forces as the earth and moon orbit each other. But apparently, it is due to the difference in the moon's gravity on opposite sides of the earth.
I got a really interesting, short but dense book recently that not just explains how the tides work, but also goes into why standing waves form just downstream from a shelf, not over it.
I have to recommend Tides, a very short introduction. Bowers and Roberts, Oxford university press.