For months, ITV News has been investigating the problem of river pollution - and the Wye, which runs from its source in mid-Wales through Herefordshire and Gloucestershire, is among the worst.
A special investigation from ITV News journalists in the Central, Wales and West Country regions examines what is going wrong - and what needs to be done.
Part one of the series looked at how high phosphate levels are damaging the river - and impacting fish stocks - while part two examined what role the poultry industry plays in river pollution.
Now, in part three of our series, ITV News West Country presenter Jonty Messer examines how sewage has contaminated the river.
What happens if you kill a river? That's the question people along the River Wye are asking - and have been asking for years.
"We're finding small dead fish washed up alongside of the river," said fisherman Peter Wright.
He has been fishing along the Wye since the 1950s but told ITV News fish stocks have dwindled.
"The amount of migratory salmon which are now entering the Wye and all of its catchment has declined dramatically since the 50s and 60s," he said.
"The quantities of fish that were being caught then were in their thousands. This year we’ll be lucky to see 200 fish caught totally in the entire Wye."
The River Wye might be an Area of Outstanding Natural Beauty - but hidden below the water's edge are storm drains.
Water companies are allowed to use the overflow network during periods of heavy rain to prevent flooding and stop sewage from backing up into people's homes.
But last year alone, the storm drains lining the rivers and streams that flow into the Wye discharged sewage 40,000 times. This means raw sewage was dumped into rivers and streams for a total of 17 million minutes - the equivalent to 33 years.
Welsh Water told ITV News it is "clear for everybody to see" the River Wye's condition is deteriorating - saying issues with storm overflows must be tackled.
But the firm said it has to "engage with customers" on how much it will cost and how long it will take to solve the problem.
Meanwhile those who live, work and rely on the river say pollution is killing it.
"We’d always had our suspicions about some of the sewage plants but not to the extent that we’ve now realised just how much is going into the water," said Nick Day, who founded the Friends of the Lower Wye alongside Mike Dunsbee.
The pair now work to raise awareness of pollution in the river - and hope to protect its future.
The pollution has also changed the way wild swimmers like Emilie Ricketts view their sport.
She now tests the water before each swim to check for levels of pollution.
"The whole idea was to be totally immersed in nature and to feel the water against your skin and the feeling that gives you," she told ITV News.
"But when you’re in there you’re actually not thinking about that any more [because of the pollution] so it’s ironic.
"I think the wildlife that we see here now, we won’t see it any more. It’s already reduced from when I had been swimming here.
"It’ll be a great shame because we’ll get to a point where everything will be gone and it’ll take decades to build it back up and the people who care won’t be around to do that."
What do the water companies say?
Steve Wilson, who is Welsh Water's managing director for Wastewater Services, said: "It is clear for everybody to see that the River Wye condition is deteriorating and that's not a good thing for anybody.
"It really matters to us - we want to make sure that the environmental impact from our operation, for producing drinking water and returning waste water to the environment, is done with as little environmental impact as possible.
"We all want rivers that we want to be able to enjoy - whether that's to fish, to paddleboard, to even swim - and storm overflows are having an impact on rivers and we've got to tackle that.
"The way the drainage network is designed, every big rain event storm overflows will operate because we've got to protect homes from sewer flooding.
"The problem is it has been going on for many years - but because we've made the data available and we're monitoring, it's all coming out.
"As an industry, we weren't really aware - we've spent a lot of money and time tackling the quality of discharges from our sewage works.
"We're not hiding from the problem but we have to engage with our customers about how much this is going to cost and how long it's going to take."