Question

Our earth is conserve with approx 75% of water still there is urgent need to conserve water

Answer 1

because all the water that you are talking about is sea water and contains a large amount of salt this water cannot be used by human and other organisms for drinking,
only a large amount of salt can be obtained from it.

Human need water which is free from salt .

Answer 2

the water covers large area but still there is need to conserve water . Because most of the amount of water is present in ocean and in the form of glaciers which is not able to drink . And only 0.5% amount of drinking water is present which is depleting with high rate so, there is need to conserve water .

hope it helps you