Answer:
Because it's in between the sea and the land
Explanation: J.K.
The word sand comes from the Dutch word Zand, which means unstable ground near a river. The modern definition of sand is based on particle size. Sand is larger than clay or silt, but smaller than gravel. The scientific community defines sand as particles with a diameter of between 0.074 and 4.75 millimeters.
J.K. again I still think it's mostly because it's in between the sea and the land.
XD