A survey of rivers in England and Wales has found that most of them don't meet up to European standards.
After testing the water, the Environment Agency discovered only five out of the 6,000 rivers are classed as being perfectly clean.
Environmental campaigners say that more needs to be done to tidy up waterways. Parts of the River Trent and Stour were in the poorest condition.
Better water quality will also provide more habitats for animals and birds.
The Environment Agency has said it'll be working hard to improve rivers over the next few years.
The RSPB and the WWF have both said much more should be done to bring back wildlife to the riverbanks.