Why does water need conservation even though large oceans surround the land masses?

Salt water of seas and oceans is unfit for consumption by humans, animals, land plants or industries. Therefore, terrestrial biota and human beings have to depend upon fresh-water resources available on land (such as water present in rain snow, springs, river, lakes, ponds and other freshwater bodies (only about 0.5% of the total water on earth). As a result, freshwater needs its conservation