Do you mean live without? Water is definitely a thing we cannot live without. 
Here's something. Hope it helps!

When the question “What is the one thing we cannot live without? “Is asked, the foremost thing us smart mouths think of is Oxygen, water and the like. Of course the answer isn’t wrong, but the question itself implies that it means something more than just the basic necessities of life. Upon giving it a deeper thought, the answer is simple and obvious. That one thing is hope. But why hope? It’s because hope is the beacon of light in times of darkness. What makes it so precious is the fact that not many people possess this valuable gift. Having something to hope for is the best thing that can happen to a person. In fact it is one of the reasons he thrives. Nothing except hope can guide a person through times of darkness. “Hope smiles from the threshold of the year to come, Whispering 'it will be happier'...” said Alfred Lord Tennyson. Indeed this is true. The only reason we push ourselves out of bed each morning, is because we hope for something to happen today. No matter how small an issue it seems, hope plays a vital role. Hope teaches to never give up. It teaches us to never stop. It teaches us to travel the road of life, no matter how hard it is. It is said that the greatest hour of darkness is just before dawn. Hope helps us to live through that darkness and emerge victorious in the end. It teaches us to succeed, to achieve and to conquer. Hope makes people love. And love is the conqueror of all hate. And only a world without hate is a world worth living for. Thus, without a trace of uncertainty, hope is the one thing we cannot do without.