The water level at the beach changes on a regular basis. What is the primary force that causes these changes in water levels?

Explanation:

The water level at the beach changes on regular basis because of high and low tides in the sea. The high tide and low tide in the sea is because of moons gravitational force on Earth. The tide are low or high depends upon the differences in how much the moon's gravity pulls on different parts of Earth. Places where pull is less experience low tide whereas places where pull is more experience high tide.