Tides depend upon the changes in the position of the moon and the sun with relation to the earth and its position; tides depend also on the effects of Earth's rotation. Other factors that determine tides are the coastline configuration, seafloor topography, weather, winds, depth of the sea floor, etc.

In part, it is the effects of the pulling and pushing of gravitational forces of the three celestial bodies --the earth, moon and the sun-- that causes tides to form. Tides can be easily predicted based on the position of these three.