About SwimZone
SwimZone gives every monitored lake, pond, and beach a single, plain answer to one question: is it safe to swim today? It exists because water quality is intensely local and changes fast, but most tools are either a nationwide map with no local detail or a thin page buried behind a state agency login. We wanted the opposite: a calm, sourced verdict you can check before you head to the water, with the reasoning shown, not hidden.
What it is
A daily read on the two hazards that close swimming spots: fecal bacteria (E. coli and enterococcus) and cyanobacteria, also called blue-green algae or harmful algal blooms. We turn public monitoring and advisories into one plain verdict, Clear to swim, Use caution, or Advisory, and the methodology explains exactly how the inputs combine. The verdict reflects the specific water you are standing at rather than a county or regional average.
What it isn't
It is a plain summary of public monitoring, not a live water test and not a safety guarantee. It tells you what the latest samples and advisories say about a place, but conditions change fast between samples. It cannot tell you the water is clean right now, and it is no substitute for your own eyes. Always look before you get in, avoid water that is scummy, discolored, or smells bad, keep children and dogs out of visible algae, and follow posted signs and local health guidance.
Where the data comes from
Nothing here is invented or scraped from other forecasters. Each spot's verdict is built from public data, cited on the pages it feeds:
- Beach advisories from EPA BEACON, the national BEACH Act database of bacteria-based advisories and closures at monitored beaches.
- Cyanobacteria from EPA CyAN, which uses satellite imagery to track blue-green algae blooms across lakes and reservoirs.
- State health and environmental dashboards, the healthy-swimming and beach monitoring programs that post bacteria results and algae advisories for local waters.
- Weather and rain from Open-Meteo: recent rainfall and conditions that often push bacteria and runoff into swimming waters between official samples.
How often it updates
The verdict is a once-daily read: it is recomputed every morning from the latest advisories, satellite passes, and local weather, so it moves with real conditions rather than minute to minute. The underlying monitoring data is refreshed as the agencies publish new results, and each page shows when it was last reviewed.
Who makes it
SwimZone is an independent project, built and maintained by a solo developer. It isn't affiliated with any government agency or the data sources it cites. It is funded by the app and subscriptions, not by ads or affiliate deals, so the verdict answers to you and not to advertisers. An iOS app with a home-screen widget and daily alerts is in the works; the website stays free.
Get in touch
Questions, corrections, or a data source we should add? Contact us. We take accuracy seriously and would rather fix something than leave it wrong.