Photo by Hannah Wright on Unsplash
NOTE: At the moment, this APP is only in BETA and is only the SE England (whilst we wait for some feed partnerships. We’d welcome your thoughts – Please get in touch if you have an opinion on the APP or would like to work with us on it.
We Built a Live Water Quality Map for Swimmers — and Discovered a Shocking Gap in the Data
The UK has a water quality crisis. Swimmers are getting sick. And almost nobody is monitoring the rivers and lakes where most of us actually swim.
Wild swimming has exploded in popularity over the past decade. Rivers, lakes, reservoirs — people are entering freshwater in greater numbers than at any point in living memory. It’s one of the most positive trends in outdoor recreation: people connecting with nature, getting exercise, building community around the water.
But there’s a problem nobody talks about enough. The water many of us are swimming in has never been dirtier — and almost none of it is being properly monitored for the one thing that makes swimmers sick: E. coli.
The numbers are stark
In 2024 alone, there were nearly one million sewage discharges into England’s waterways — one every 30 seconds. Water companies paid shareholders £1.2 billion while dumping 4.7 million hours of sewage into our rivers, lakes and coastal waters.
The human cost is real. Surfers Against Sewage received 1,853 illness reports from water users in 2024 — an average of five people getting sick every single day after entering UK water. From stomach bugs to hospitalisations. One sea swimmer from Bognor Regis ended up in critical care needing open-heart surgery. An Ironman athlete was left unable to train for months.
The number of bathing spots rated “Poor” — the lowest category — doubled between 2023 and 2024, from 18 to 37. A slight improvement in 2025 means nothing when the underlying infrastructure is broken.
Surfers Against Sewage have done extraordinary work bringing this crisis to public attention for coastal swimmers and surfers. But what about the people swimming in rivers and lakes?
The gap nobody is talking about
We spent months trying to build a tool that could show wild swimmers real, live water quality data for rivers and lakes. We contacted the Environment Agency, dug into every public dataset, tested every API, spoke to researchers and community monitoring groups.
What we found was genuinely surprising.
There is no live, publicly available E. coli data for rivers and lakes in England.
None. Not from the Environment Agency, not from any government body, not from any public platform.
The EA’s Bathing Water Quality programme — the only system that publishes real E. coli readings — covers 451 designated bathing sites across England. Almost all of them are coastal beaches. The programme exists because EU legislation required it for coastal tourism sites. Rivers and lakes were largely left out.
If you want to know whether Brighton Beach is safe to swim in, the EA tells you every week during summer. If you want to know whether the River Wey in Guildford — where thousands of people swim every summer — is safe today, the answer is: nobody officially knows. The data doesn’t exist.
We tested the EA’s Water Quality Archive API — a vast database of over 72 million water quality observations. We searched for every E. coli and coliform determinand code in the system. The result: zero observations. The archive holds physical and chemical data — pH, phosphates, dissolved oxygen — but no bacteriological data for freshwater at all.
This is a systemic failure. The rivers and lakes where wild swimming is growing fastest are precisely the places where monitoring is most absent.
What we’ve built
Today we’re launching the SE England Water Quality Map — a free, public tool that brings together every credible live data source we could find for swimmers in South East England.
What’s in it
🦠 Live E. coli data — weekly Environment Agency bathing water readings for coastal and river designated sites across SE England, colour-coded against EU Bathing Water Directive thresholds. Updated throughout the May–September bathing season.
🌊 Real-time river levels — live gauge readings from the Environment Agency’s flood monitoring network, the same data that powers GaugeMap. Critically, rising river levels after rain predict E. coli spikes within 24–48 hours — the app makes that connection explicit.
🌿 Blue-green algae sightings — community-reported BGA observations for SE England. We’re working with UKCEH to integrate their Bloomin’ Algae iRecord feed as the official data source. Until that integration is complete, the BGA layer shows community reports and is clearly labelled as such.
🦦 River health observations — Big River Watch data from The Rivers Trust, covering citizen science surveys of river health, pollution sightings and water condition across SE England rivers.
What’s not in it — and why
We’re not showing data we don’t have. There’s no freshwater inland E. coli layer because that data doesn’t exist as a live feed anywhere. We’d rather be honest about the gap than fill it with numbers that look authoritative but aren’t.
What we’re doing about the gap
We’re not stopping at building the map. We’re actively working to help fix the data problem.
Water Rangers and CaSTCo — We’ve reached out to Water Rangers, the citizen science platform behind CaSTCo (Catchment Systems Thinking Cooperative), a national collaboration of 33+ organisations building community water monitoring across the UK. The River Wey Trust and ZERO Guildford‘s community lab — in partnership with the University of Surrey — are already producing monthly E. coli readings for the Wey catchment using ISO-certified methods. We want to display that data, with full attribution, as the foundation of a community freshwater monitoring layer.
UKCEH — We’ve applied to integrate with the iRecord API that powers Bloomin’ Algae, which would give us verified, UK-wide BGA data automatically.
Community submission — We’re building a feature that lets anyone submit their own test kit results directly to the map. If you’ve tested your local river with one of our E. coli kits, your reading belongs on the map. Over time, that community dataset could become the resource that government hasn’t built.
The bigger picture
Surfers Against Sewage did for surfers what nobody had done before: gave a community real-time information about the water they were about to enter, and turned that information into political pressure for change.
Wild swimmers deserve the same. The rivers and lakes where we swim aren’t secondary — they’re where the next generation of water users is discovering the outdoors. They deserve the same scrutiny, the same monitoring, the same public accountability that coastal beaches receive.
The water quality map at app.wildswimmingtests.co.uk is a start. It’s genuinely useful right now for the data it has. But it’s also a statement about what’s missing — and an invitation to anyone with data, expertise or community reach to help us build something better.
If you run a river monitoring programme, work in water quality data, or represent a community group testing your local water — we want to hear from you.
And if you swim in rivers and lakes — test your water. Submit your results. Help us build the dataset that doesn’t exist yet.
The SE England Water Quality Map is free to use at app.wildswimmingtests.co.uk. Data sources: Environment Agency Bathing Water Quality API · EA Flood Monitoring API · The Rivers Trust Big River Watch · UKCEH Bloomin’ Algae (integration pending). All data is clearly attributed and dated. We don’t show data we don’t have.
wildswimmingtests.co.uk sells water quality test kits for open water swimmers and venue operators across the UK.
