Your Ultimate Guide to Choosing the Best Times and Locations for Open Water Swimming

Open water swimming can be a refreshing and invigorating pastime, yet it carries inherent risks that every swimmer should be aware of. Prior to embarking on your aquatic adventure, it is essential to understand the monitoring processes for water quality in England, including the areas where such monitoring is applicable and where it is not.

Understanding Designated Bathing Waters

A designated bathing water refers to an officially recognised swimming location—be it a beach, lake, or river—subject to regular testing and monitoring for harmful bacteria that can impact human health, as outlined in the Bathing Water Regulations. Currently, England boasts 464 designated bathing sites, which are sampled from May through to September. This systematic monitoring ensures that vital information regarding water quality is readily available to aid swimmers in making informed decisions about their swimming locations.

However, it is important to recognise that being designated does not inherently guarantee good water quality. Rather, it provides access to reliable, up-to-date information regarding the water conditions, a significant advantage over locations that lack such monitoring and where the risks associated with harmful bacteria remain uncertain.

Risks of Non-Designated Bathing Waters

As the popularity of open water swimming continues to rise, many enthusiasts are drawn to lakes, rivers, and coastal areas that are not classified as designated bathing waters. These locations are not routinely monitored for water quality, resulting in heightened uncertainty and risk for swimmers.

Non-designated waters lack the systematic oversight seen at bathing water sites, meaning that there is no equivalent resource to Swimfo to provide insights into water quality. Conditions can change rapidly due to various factors, including rainfall, river flows, tides, and wind—all of which can introduce pollutants. Sources of such contamination may include agricultural runoff, urban drainage, road pollutants, and sewage discharge, all of which can carry harmful bacteria. Following rainfall, the likelihood of pollution entering rivers increases, while elevated water levels and faster flows can further compound risks for swimmers.

Most rivers are managed with multiple objectives in mind, such as wildlife protection and water usage, rather than adhering to bathing water standards. The bacteria that can adversely affect human health do not pose the same risks to aquatic fauna, which is why monitoring protocols are not applied beyond designated bathing waters.

In response to public demand for cleaner and more accessible river swimming, six of the thirteen new bathing waters designated for 2026 are rivers. These locations will now be monitored and assessed against established bathing water standards, allowing for the identification of faecal pollution sources and facilitating necessary improvements.

Staying Safe Around Weirs and Locks

The Environment Agency is responsible for managing flood risk, water resources, and navigation assets across England, which includes weirs, sluices, locks, and pumping stations. While these structures are crucial for effective water management, they also pose significant hazards for swimmers.

Weirs can generate powerful recirculating currents, known as stoppers, that can pull individuals underwater and trap them against the structure. Sluices have the potential to open and close without warning, resulting in sudden surges of water that can easily overwhelm even the most proficient swimmers.

Locks and other navigational structures also present risks. Water levels can fluctuate rapidly with the opening and closing of lock gates, creating strong flows and turbulence. Additionally, the unexpected entry or exit of boats can increase the likelihood of collisions, posing further dangers for anyone in the water. It is advisable to maintain a safe distance from these structures and adhere to any posted safety signage.

Benefits of Monitoring Designated Bathing Waters

The Environment Agency offers a complimentary service called Swimfo, which provides the latest information on all 464 designated bathing waters across England. This resource includes annual classifications of water quality, pollution risk forecasts, and monitoring results. Swimmers can search for specific locations to ascertain whether a site is rated as Excellent, Good, Sufficient, or Poor, as well as check for any predictions of decreased water quality on the day they plan to swim.

From mid-May to the end of September, the Environment Agency conducts over 7,000 tests on designated bathing waters, searching for bacteria that indicate faecal contamination. However, it should be noted that these tests do not determine whether the contamination originates from human sources, such as sewage, or from animals, including birds, dogs, or livestock.

Swimfo also offers a pollution risk forecasting service, which alerts users to conditions such as rainfall, wind, and high tides that may temporarily affect water quality or indicate a pollution incident. In 2025, 93% of designated bathing waters met the minimum standard of Sufficient or above—a promising overall result, although conditions can vary rapidly, making pre-swim checks essential.

Environmental Agency’s Role in Water Quality Management

The Environment Agency is actively involved in monitoring and classifying bathing waters, investigating pollution incidents, and regulating a variety of activities that impact water quality. Every storm overflow in England’s sewage network is now equipped with monitoring devices, providing an unprecedented national overview of water company discharges. In instances of illegal discharges, the Agency is empowered to take enforcement actions, including potential criminal prosecution.

However, the sources of pollution are numerous, necessitating collaborative efforts from water companies, farmers, local authorities, and other stakeholders to enhance water quality. In cases where bathing waters are classified as Poor, the Agency works alongside partners to identify causes and explore opportunities for improvement.

If you observe suspected pollution, it is crucial to report it. Such reports assist in investigating incidents and targeting appropriate responses.

Essential Pre-Swimming Checks

Before you take the plunge, it is advisable to consult Swimfo for the most current information regarding designated bathing waters. Remember that non-designated areas are not consistently monitored for water quality, and recent rainfall may elevate risks in many locations. For comprehensive safety advice, consult the Swim Healthy page on GOV.UK and the RNLI’s open water swimming safety guidelines.