Water pollution occurs when harmful substances contaminate bodies of water, including lakes, rivers, oceans, and groundwater. It negatively impacts both the environment and human health. There are two main types of water pollution: point source pollution which comes from identifiable sources like pipes or drains, and non-point source pollution which has diffuse origins like agricultural runoff. Water pollution can be caused by improper disposal of waste, excessive use of fertilizers and pesticides, and littering near water sources.