Dumping of wastes-
1) Industrial wastes and medical wastes toxify the water.....
2) domestic waste and sewage waste end up in the rivers, ponds, lakes making them unfit to call them as water..
3) villagers use riverbeds to wash animal waste, take bath, recreation, dumping of other animal excreta along with dead bodies
4) all the above causes kills marine life and the unchecked dead marine life also stay dumped in the waters.......
industries throw hot , toxified liquids into water bodies