Near shore, water appears to come in during the flood tide and go out at ebb tide. In fact, high tide is the crest of the tide wave, which is 6 feet higher than the low tide, which is the trough of the tide wave. The position of the moon during its month-long trip around the earth alters the height of the tides. When the sun, the earth, and the moon are lined up at the time of a full moon or a new moon, the combined gravitational pull of the sun and moon create spring tides. When the moon is in the first and third quarters, the sun, moon, and earth make a right angle, and the sun and moon pull on the ocean waters from different directions, creating neap tides.
Spring tides are bigger, with higher high tides and lower low tides than neap tides.
In addition to gravity, tides are affected by centrifugal force caused by the earth's spinning. As a result of this force, tides have a slightly circular motion. In shallow inshore waters, tidal currents can greatly affect boating, fishing and other activities on the coast. Offshore, on Gray's Reef, the tide is much less noticeable. The energy driving the major ocean currents comes from winds.