Tides are caused by the gravitational pull of the moon and sun, along with the rotation of the earth. All surfaces of the earth are pulled towards the moon and the sun. As the earth rotates, the moon’s gravitational force continually mounds the water and that fluid mound moves around the earth. It has a great and obvious effect on the water of the earth’s oceans. The maximum water level is called high tide and the minimum water level is called low tide. The time between high and low tides, when the water level is falling is called the “ebb”. The time between low tide and high tide, when the water level is rising, is called the “flow”. The actual height of the tide is influenced by the shape of the coastline and depth of the water.

The highest tides in the world are at the Bay of Fundy, Canada. At some times of the year the difference between high and low tide is 16.3m, which is taller than a three storey building.