Question

earth is covered with 75percentage of water but we need to save water justify your answer

Answer 1

because we have only few percent of fresh water which can be used for our daily purposes, rest is all salty water which we can't use for our daily purposes. that's why we need to save water

Answer 2

it is not the quantity of water that matters for the fulfillment of need of water but it is the quality that matters .
oceans or you can say marine water has high salt content making it improper for drinking purpose.
only the ground water or rain water is considered proper . if you think of pollution then you must know what have pollution caused to our rivers .
element composition is also a major factor which decides water quality suitable for drinking .