Tides are the periodic rise and fall of the water level in the sea that occurs at regular intervals twice a day. Tides are experienced in large bodies of water suck as oceans and seas. When the level of water rises, it is high tide and when the level of water is low it is low tide. Tides are caused by the gravitational pull of the Moon and the sun. Even though the Moon is much smaller than the Sun, it exerts a much larger gravitational pull. This is because its distance from the Earth is less compared to that of the Sun. The height of the tides is not the same on every day of the Month. It depends on the relative position of the Moon and the Sun with respect to the Earth. During the full moon day known as Purnima in India and the new Moon day known as Amavasya in India, the Earth, Moon and the Sun are in the same straight line. The Moon and the Sun exert their combined gravitational pull in the same direction, resulting in extra high tides.