71% of the tarth to covered with water.
The heat of the sun increases the temperature of the ocean surface, which causes the water to evaporate and form clouds. The clouds showers water in the form of rain on the land. Most of this water flows from the surface of the land through rivers and reaches the ocean. Water is stored in the ground as underground water, which finally merges with the sea through rivers in the form of springs.
→In this way, the water becomes available for living organisms as it is the system of nature and finally reaches back to the ocean.