Each day, the ocean water rises and falls at different times. This movement of water is known as a tide. A tide is a change in water level at the shoreline. Tides are caused by the pull of gravity between Earth and the Moon and Earth and the Sun. During each 24-hour period, most beaches around the world will have two high and two low tides.
The Moon’s gravity has a powerful effect on Earths waters. In fact, it is far more powerful than the Suns because the Moon is closer to Earth than the Sun. The Moon pulls the water toward itself.
When the gravitational force of the Sun combines with the gravitational force from the moon it can increase a high tide by making it rise higher than normal. This will happen when the Moon is either in its new moon or full moon phase.
Each month most locations on earth experience 2 spring tides and 2 Neap tides.
Spring Tides: When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low.
Neap Tides: During First and last quarter the sun and moon work at right angles, causing the bulges to cancel each other.The result is a smaller difference between high and low tides and is known as a neap tide.