Moon

The gravitational pull of the Moon influences our oceans' tides more than the Sun because it is much closer to the Earth. High tides are created by the moon pulling water up, and low tides are created by water moving away to satisfy those high tides. High and low tides occur almost twice per day, but not quite. This is due to the fact that one solar day is 24 hours, but a lunar day, the time it takes the Earth to reach the same position relative to the Moon, is about 24 hours and 50 minutes. The tides follow a lunar day schedule because the gravitational pull of the Moon is almost twice as strong as that of the Sun. 

The change between tides, also known as the flood tide and ebb tide, are gradual. This means that the line between the high and low tides is a gray area, so one cannot exactly predict the length of each. The speed of water flow varies during te flood and ebb eriods, and it also varies from place to place.