England's rivers are contaminated by a "chemical cocktail" of sewage, agriculture and road pollution, according to MPs.
Microplastics, slurry, car tyre particles, oils and wet wipes are all part of the problem, they said.
Why do we need to protect our water?
High quality water is key both to our survival and that of the environment.
Each person in the UK uses around 140 litres of water a day for washing, drinking and cooking.
The water we use in our homes is safe, but increased pollution means more intensive treatment is required, which raises household bills.
Contamination also threatens water sources crucial for the survival of wildlife, the natural environment and the food system.
According to the Wildlife Trusts, rising pollution levels place 10% of freshwater and wetland species at risk of extinction. In Wales and England, 38% of fish health checks are failed due to disease caused by pollution.
These species are vital to:
reduce the impact of flooding
provide income for communities: the UK's freshwater fisheries provide £1.7 billion to the economy
support food and agricultural services
Access to clean water sources can also provide an opportunity for outdoor exercise.
Where does pollution come from?
The main causes are:
excessive use of fertiliser and pesticides in agriculture - which is responsible for 40% of water pollution in England
untreated sewage released by water companies - responsible for 35%
"run-off" from roads and towns which contains pollutants such as oil - responsible for 18%
Professor Steve Ormerod, an ecologist at Cardiff University, warns of other threats. He says: "We need to understand the risks which come with emerging pollutants - pharmaceuticals, microplastics. We don't know, at this stage how big a problem they're going to be."
Previous campaigns on acid rain and sewage have been successful in improving water quality, but improvements have stalled since 2016.
"The fact remains that many water companies, farmers and others are still not doing enough to protect [our waters]," the Environment Agency says.
Which areas are most affected?
Scotland has the largest number of high quality rivers - with up to 66% in good condition.
In Wales, the figure is 40%, in Northern Ireland it's 33% and in England it's just 14%.
Pollution by water companies is particularly high in the south and southwest of England.
Access to good quality water sources also varies across income groups.
The Environment Agency says "people in deprived and heavily populated urban areas were more likely to live within 600m of a river with poor chemical or biological quality".
This could be because these communities are more likely to live in areas near heavy industry and sewage treatment works.
Campaigning groups including Surfers against Sewage now provide real time data on water quality to help people assess the quality of water sources near them.
What's being done to tackle the problem?
In 2018, the government published its 25-year Environment Plan, supported by a new Environment Bill for England which was designed to strengthen rules.
However the bill was only approved in November 2021, after a lengthy battle over how much sewage can be released into rivers. Environmental campaigners and peers in the House of Lords argued the bill was too lenient on water companies.
The UK's national environment agencies are meant to monitor the quality of water to ensure industry compliance against the existing regulations.
However, chairman Philip Dunne said the Environmental Audit Committee's inquiry uncovered "multiple failures in the monitoring, governance and enforcement on water quality," carried out by England's Environment Agency.
Since 1993, the number of water quality samples taken annually by the Environment Agency and Natural Resources Wales has dropped by 57%, which the committee says is a result of budget cuts.
The National Farming Union, believes improved cooperation is key. It cites the example of Poole Harbour Nutrient Management Scheme, where farmers are paid by Wessex Water to minimise fertiliser run-off, reducing contamination and therefore water treatment costs.
But responding to the report, Professor Hannah Cloke, professor of hydrology at the University of Reading said: "Collaboration is fine but will mean nothing without investment. We need to get real. This problem has arisen because of chronic, long-term under investment."
England and Wales' water companies have promised to invest £4bn by 2025 to reduce sewage leaks.
However, last year BBC Panorama revealed that they continued to allow undiluted sewage into waterways. This prompted calls by MPs for a move away from a system where water companies self-report breaches.