Every half hour, this site reads the official warnings and the live sewage overflow feeds for all 941 designated bathing waters in Britain and Ireland, and works out a single answer for each one.
How a verdict is decided
- Don't swim today — an official warning is in force, or a monitored storm overflow is discharging within 2km right now.
- Take care — the regulator forecasts increased pollution risk, or an overflow discharged nearby in the last 48 hours, or heavy rain has fallen at a beach known to be affected by it.
- No warnings today — the checks that could be made were made, and none of them found anything.
- Can't say today — something could not be checked: a feed was down, a nearby overflow monitor was not reporting, or the bathing season has ended and the daily forecasts have stopped.
Each beach lists what was actually checked and what wasn't, so a green tick is never a bare assertion. Four rules the code holds to:
- Never show green because something failed. A dead monitor, a feed that is down or a season that has ended all produce “can't say”.
- An official warning outranks anything calculated here.
- Last season's classification is not evidence about today's water. It can add a warning; it never earns a green tick on its own.
- Say when, and say whether a number was measured or modelled.
What it can't tell you
- Ireland has no sewage spill monitoring at all, north or south. There is no monitoring programme to read. For Irish beaches this shows official notices and sample results only — an empty spill list there means nobody is measuring.
- Scotland forecasts 30 of its 90 beaches. The rest have last year's rating and nothing about today.
- The season ends. Daily forecasts and weekly sampling stop in mid-September in Scotland and Ireland, and at the end of September in England and Wales. Out of season the site says so rather than showing green.
- Only monitored overflows appear. Unmonitored pipes, farm run-off, misconnected drains and boats do not. A monitor that has stopped reporting counts as unknown, never as clean.
- Distance is not a model. A spill within 2km counts against a beach; tides and currents decide what actually reaches the water. Southern Water's own tidal assessment is used where they publish it.
- Rainfall is modelled, from a weather model on roughly an 11km grid — not a rain gauge at the beach.
Where the data comes from
- Environment Agency — daily pollution risk forecasts, open pollution incidents, suspensions and classifications for England
- Natural Resources Wales — the same for Wales
- SEPA — Scottish classifications and daily predictions
- DAERA — Northern Irish sampling
- EPA Ireland and local authorities — classifications and statutory bathing restrictions
- Thames, Southern, South West, Wessex, United Utilities, Yorkshire, Northumbrian, Anglian, Severn Trent, Dŵr Cymru Welsh Water and Scottish Water — live storm overflow status for 18,600 monitored outfalls
- Open-Meteo — rainfall
The code that collects it is public: Leiglow/swim-collector.
This is not an official source
It reads published data and presents it plainly. It is not a substitute for the regulator, the water company or a sign at the beach. If a sign says otherwise, believe the sign. Nothing here is advice about whether you personally should swim.