Many organisms, especially the California grunion, time their reproductive cycle to coincide with the tides. Forces Tides are the periodic variations in sea level caused by the gravitational attraction of the sun and the moon on the Earth. The force of this attraction creates very predictable rises and falls in sea level as the Earth rotates on its axis. When sea level is at its greatest height, the tide is said to be high. When sea level is at its lowest extent, the tide is said to be low.
High tides bring water far up on the shore.
When wave action is high, these high tides may damage homes and undercut sea-side cliffs. On the other hand, low tides expose great expanses of the beach. The gravitational attraction of the sun and the moon on the Earth depends on the distance of these bodies from the Earth. The closer two planetary bodies, the greater their gravitational attraction. In general, the moon has about twice the effect on our tides than the sun.