Each and every day without fail and regardless of what is happening in our world, Hilton Head Island (and most---but not all coastal areas) experiences two high tides and two low tides within a 24-hour period. Our tides are somewhat unique in that they can rise or fall more than 8 vertical feet in only 6 hours, though the average rise and fall is about 6.5 feet. Compare this with offshore (in the deep ocean) tides which have a tidal change of less than 1.6 feet---or to the tides at the Equator (they are are nonexistent)!
The word “tide” defines the alternating rise and fall in sea level with respect to the land. Tides are the periodic rise and falling of large bodies of water. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon with another bulge occurring on the opposite side. As the sun, moon and Earth interact, ocean levels fluctuate. Since Earth spins once every 24 hours, it will pass through both bulges of water each day. The sun and moon, shape of a beach, angle of a seabed leading up to land, and prevailing ocean currents and winds will affect the height of a tide.
The phase of the moon---either full or new---can cause the tide to rise even higher due to the increased gravitational pull on the earth. These larger tides are called spring high tides, though they have nothing to do with the season of new beginnings. Around each new full and new moon, the sun, Earth and moon arrange themselves more or less in a line, creating exceptionally strong gravitational (or tractive) forces. The pull on the tides increases because the gravity of the sun reinforces the moon’s gravity. Spring tides are about 20% higher than normal tides and occur any time of the year. On the night of a full moon, however, Island high tide will always occur around 7 pm EST.
Posted by Christina Galbreath-Gonzalez
The lower tides, called Neap tides, occur when the sun and moon are not aligned. The gravitational forces cancel each out so the tides are not as dramatically high and low. It is the tide’s range at its minimum since the sun’s gravity is working against the gravity of the moon. These tides occur halfway between each new and full moon when the sun and moon are at right angles as seen from Earth, and the result is a smaller difference between the high and low tides. There is a seven-day interval between spring tides and neap tides