Quote by Divine_Warrior
The gravitational pull of the moon tugs on the surface of the ocean until its surface mounds up and outward in the direction of the moon. When the mound of water has reached it's highest point it is called a high tide. On the opposite side of the Earth from the moon, the centrifugal force caused by the Earth's rotation produces another mound of water and high tide. Between these two high tides are two flat areas on the surface of the ocean which are the low tides. Each day there are two high tides and two low tides. The time between high tide and low tide is a little under 6 hours and the entire tidal cycle repeats itself four times each day. The regularity of the tides corresponds to the regular of the Moon around the Earth and he rotation of the Earth as it orbits around the Sun. Depending on the position of the Moon relative to the Earth and Sun, a moon can have different phases. The phases of the Moon are also very regular, and have been used for thousands of years to keep track of time using the lunar calendar. In addition to the daily movements of the Moon, these monthly lunar cycles can also impact the tides. (Sorry for geeking out on you.)