By Roland Pease
BBC science correspondent
Tuesday is the UN's World Water Day, marking the start of an international decade of action, Water For Life.
Rivers that cross frontiers can lead to water disputes
The decade is aimed at achieving one of the UN's millennium development goals - halving the number of people without clean water supplies by the year 2015.
One person in six has no access to clean drinking water and one in three has no access to sanitation.
But water is about more than thirst and cleansing. Two-thirds of water is used in agriculture - half of it wastefully.
Water should be the key to life. But each year for more than three million people, it is the cause of death - because contaminated and stagnant water delivers deadly typhoid, cholera, malaria and diarrhoea to homes around the world.
Using water wisely is central to feeding the world; and competition for water has the potential to cause conflict.
QUEST FOR WATER
Fetching water is estimated to take up 40bn hours a year in Africa
Unsafe water and poor sanitation are blamed for 80% of all sickness globally
Great rivers like the Danube, the Nile, the Tigris and Euphrates, and the Brahmaputra cross national boundaries, resulting in disputes over priority in the use of their water.
Will the decade of action achieve its goals? Cynics are weary.
As one expert told the BBC, the problems are well known, but actually, despite the brave words, the world does not care enough about water.