Water is the main source of our lives,without water,we will not survive. Now alot of mankind have pollute the water,which change it into sewage that contains human waste,detergent & chemicals.Peoples that are poor are forced to drink the polluted water.
The example of human pollution on our waters are by littering & oil spill. With seas & rivers polluted,it will have an impact on sea animals such as seagulls,for example,when birds dive down towards the sea to catch fish,the oil will sticks to their fur which removes the air trapped by the feathers & fur which functions as a layer of insulation for the animal causing them to freeze to death in the cold. 
Littering,by littering at the rivers or beaches it can cause economic loss, as we litter,the fishes die,as the fishermen's livelihood as well as the fishing industries will have no fishes to fish & the fishermen may die of hunger as they can only afford to fish. People in a village may swim or bath in the river that are littered which is very dangerous as they can injure themselves.
