As technology improves scientists are a to detect more pollutants at smaller concentrations in Earths freshwater bodies. Oil rigs are a big problem with water pollution because they suck pall the oil out of the ground but when it hits open water some can manage to get out and get into the ocean with sea creatures like fish and pelicans can get stuck in, fish have to suck in water to live so they are sucking in the oil and thats not good because it can kill them. With the construction of buildings in cities by the water can get dust and other things like that in the water, the reason why people are getting so upset about this is because in the future we could maybe find a way to make salt water into freshwater but if all that salt water gets polluted then there will be no more salt water to make freshwater. In foreign countries people are secretly sucking freshwater out of freshwater bodies to keep for them selfs and if they keep doing that there will eventually be no more freshwater for other people.
Safari national geographic website