About this site
What it is, where the numbers come from, and what it cannot tell you.
What it is
Can I Swim? answers one question for every designated bathing water in Britain and Ireland, and for the named waterfalls in between: is it sensible to get in today? It reads the official pollution forecasts, the water companies' live storm overflow monitors and recent rainfall every half hour, and works out a single answer for each place, with its reasons and its gaps shown.
There is no account to make, nothing to install, no advertising and no tracking. It sets no cookies and makes no third-party requests other than the map tiles and one webfont.
Who made it, and why
It was built by Jay Horwood, in Hertfordshire, after looking for a straight answer about a beach and finding either an app, a login, or a map that would not say what it did not know. It is not a company and nobody is paid for it. The running cost is a domain name.
The design rule throughout is that the site would rather say “can’t say” than guess. A reading that could not be taken is shown as a reading that could not be taken — never as an all-clear.
Where every number comes from
- England — Environment Agency: daily pollution risk forecasts, open pollution incidents and bathing water classifications.
- Wales — Natural Resources Wales, through the same service.
- Scotland — SEPA: daily predictions for the beaches that get them, and annual classifications for the rest.
- Northern Ireland — DAERA sample results and bathing advice.
- Ireland — the EPA and local authorities: statutory bathing restrictions and sample results.
- Storm overflows — the eleven water companies that publish live monitor status, about 18,600 outfalls in all.
- Rainfall — Open-Meteo, modelled rather than measured, and labelled as such wherever it is used.
- Waterfalls — OpenStreetMap contributors, under the Open Database Licence.
- Photographs — Wikimedia Commons, each credited to its photographer on the page it appears.
Every reading on the site carries the source it came from and the time it was taken. If a source is unreachable, the page says so rather than falling back on something older and pretending it is current.
What it cannot tell you
- It is not a substitute for the sign at the beach. A warning posted on site by the regulator or the council is the one that counts.
- Nowhere in Ireland monitors storm overflows. No such programme exists, so for Irish waters sewage discharges genuinely cannot be checked — the site says this on every affected page rather than showing a clear result.
- A monitor can be offline. A silent monitor is not a quiet one, and is counted as unknown, not as clean.
- Waterfalls are not tested by anyone. Their pages answer whether there is water coming over, never whether it is safe to swim.
- Nothing here is a laboratory result for today. Water is sampled every few weeks, not hourly; forecasts are models.
Something wrong?
Corrections are welcome and wanted — a beach in the wrong district, a waterfall under the wrong name, a verdict that does not match the sign in front of you. Please say which place and what you saw.
Or use the Seen something? form on any beach or waterfall page, which records which place you meant.
Reports go into a queue and are read by a person before anything appears on the site. Nothing you send is published automatically.
For journalists
Everything here is derived from published open data and can be checked against the sources above. The code that collects it is public, so any figure on the site can be traced from the page back to the regulator that issued it. Happy to help with specific questions, figures for a given stretch of coast, or historical context.
The code
The collector is open source at github.com/Leiglow/swim-collector. It runs every half hour and publishes one small snapshot; there is no database of readers and nothing personal is stored anywhere in it.