What is something that's gets in the water that isn't supposed to be there?

One common example of something that gets into water sources and isn't supposed to be there is plastic pollution. Items like bottles, bags, and microplastics can harm aquatic life and disrupt ecosystems. Additionally, pollutants such as chemicals from agriculture, pharmaceuticals, and sewage can contaminate water, posing risks to both human health and the environment. Effective waste management and pollution control measures are essential to prevent these substances from entering our waterways.