water is necessary for life.All organism contain in, some drink it and some live in it.Plants and animals require water that is moderately pure. and they cannot survive. if water contains toxic chemical or harmful microorganism . Water pollution kills large quantity of fish, birds, and other animals, in some cases killing everything in an affected.So it is very important clean water.Water pollution occurs mostly, when people overload the water environment such as streams, lakes ,underground water ,bays or seas with waster or substances harmful to living beings.pollution makes streams, lakes and coastal waters unpleasant to swim in or to have a rest. Fish and shellfish harvested from polluted waters may be unsafe to eat. People who polluted water can become ill, if they drink polluted water for a long time.