Answer
Tides are produced by differences in gravitational forces from one side of a body to the other. The ratio of the distance from an overhead melon to one’s feet vs. to one's head is large, and so the difference in gravitational force is large.
For the moon, the ratio of the distance to the head to the feet is essentially the same. The melon causes more tidal effects than the massive, distant moon.
This is discussed on page 169.
