Food is necessary for a living; water is also necessary for living. None seem to be more superior to the other. As a matter of fact, water is classified as a part of the classes of food nutrient. Also, water is of a large and important constituent in foods, either raw or cooked. So, it is not really acceptable or palatable to separate food and water as necessities for living. Though, water seems to be of a higher constituent in the body than other nutrients of the food. And it is discovered living longer without food than without water.
It can take any human barely a week to live without water, but one can still live up to or even more than four weeks without food. But that does not really mean that one is necessary, while the other is not. No! They are both necessary for living. To live long, take healthy food in the right proportion, and drink a lot of water.