Open water swimming can be an invigorating experience, but it carries real risks. Before you head out, it's worth knowing a little about how water quality is monitored in England and where that monitoring does and doesn't apply.
In this blog, we explain where you can find information to help you decide where and when to swim, and why not all swimming spots are equal when it comes to water quality.
What does it mean to swim at a designated bathing water?
A designated bathing water is an officially recognised swimming spot - a beach, lake or stretch of river - that is regularly tested and monitored for bacteria that can affect human health as set out in the Bathing Water Regulations. In England, there are currently 464 of these sites, sampled between May and the end of September so that information is publicly available to help you make informed decisions about where and when to swim.
Importantly, designation does not mean water quality will always be good. What it does provide is access to reliable, up-to-date information about that water - a significant difference from swimming somewhere that isn’t monitored for the types of bacteria that can impact human health.
What are the risks of swimming at non-designated bathing waters?
As open water swimming grows in popularity, many people enjoy swimming in lakes, rivers and coastal spots that are not designated bathing waters. These places are not monitored for bathing water purposes and therefore carry a greater level of uncertainty and risk.
Non-designated waters are not routinely monitored for bathing water quality, and there is no equivalent of Swimfo to tell you what the water quality is likely to be.
Water quality can change quickly. Rainfall, river flows, tides and wind can all affect conditions. Pollution can come from a range of sources, including agriculture, urban drains, roads and highways and sewage discharges, all which can carry harmful bacteria. After rainfall, there can be a greater likelihood of pollution entering rivers, while water levels and flows may also be higher and faster, increasing potential risks for swimmers.
Most rivers are managed for a range of purposes, including protecting wildlife and supporting water use, rather than specifically meeting bathing water standards. The bacteria that can affect human health are not damaging to fish or other water organisms, which is why we don’t routinely monitor for them away from designated bathing waters.
Six of the 13 new bathing waters designated in 2026 are rivers, reflecting public demand for cleaner, accessible river swimming. These are now being monitored and assessed against bathing water standards. Monitoring helps identify sources of faecal pollution and inform action where improvements are needed.
Wherever you choose, there are simple things you can do to reduce the risk of getting sick if swimming in open waters, such as not swimming after recent rainfall. There is more advice on this if you search ‘Swim Healthy’ on Gov.uk.
Dangers to swimmers around weirs, sluices and locks
The Environment Agency manages flood-risk, water-resource and navigation assets across England, including weirs, sluices, locks and pumping stations. While these structures play an important role in managing our waterways, they can pose a serious danger to swimmers.
Weirs create powerful recirculating currents, known as stoppers, which can pull people underwater and trap them against the structure.
Sluices can open and close automatically without warning, releasing sudden surges of water that can quickly overwhelm even strong swimmers.
Locks and other navigation assets can also be hazardous. Water levels can change quickly as lock gates open and close, creating strong flows and turbulence. Boats may enter and leave unexpectedly, increasing the risk of collision or injury for anyone in the water.
If you are thinking of cooling off in the water this summer, stay well clear of these structures and always follow safety signage.
What’s the benefit of checking bathing water quality at designated bathing water sites?
The Environment Agency's free Swimfo service gives you the latest information on all 464 designated bathing waters in England, including annual water quality classifications, pollution risk forecasts and monitoring results. You can search by name or location to see whether a site is rated Excellent, Good, Sufficient or Poor, and check for any predictions of reduced water quality on the day you plan to visit.
From mid-May to the end of September, the Environment Agency tests designated bathing waters over 7,000 times, looking for bacteria that indicate faecal (poo) contamination. It doesn’t indicate whether that contamination comes from human sources, such as sewage, or animals such as birds, dogs or farm livestock.
Swimfo also includes a pollution risk forecasting service, which flags when factors like rainfall, wind and high tides may temporarily affect water quality or we identify a pollution incident.
In 2025, 93% of designated bathing waters met the minimum standard of Sufficient or above — a strong picture overall, however conditions can change, so checking before you go is always worthwhile.
What the Environment Agency is doing
The Environment Agency monitors and classifies bathing waters, investigates pollution incidents and regulates a range of activities that affect water quality.
Every storm overflow on the sewage network in England now has a monitor fitted, giving the most complete national picture of water company discharges to date. Where evidence of illegal discharges is found, the Environment Agency can take enforcement action including criminal prosecution.
We know though that there are many sources of pollution. Improving water quality requires action from water companies, farmers, local authorities and others. Where bathing waters are classified as Poor, we work with partners to understand the causes and identify opportunities for improvement.
If you spot suspected pollution, report it to us. Reports help us investigate incidents and target our response where necessary.
Before you swim
Before you swim, check Swimfo for the latest information on designated bathing water. Remember that non-designated waters are not routinely monitored for bathing water quality, and that recent rainfall can increase risk at many locations. For detailed safety advice, visit Swim Healthy on GOV.UK and the RNLI's open water swimming safety guidance..
seen at 16:46, 10 July in Environment Agency: For homes and habitats..