Shocking new data revealed that the Serpentine Lido in Hyde Park, London, saw a 1,188% rise in faecal contamination and spike in E.coli levels last year, a strain of bacteria that can cause diarrhoea, fever, stomach cramps and, in the most extreme cases, kidney failure. The Lido recorded an E.coli contamination count of 45 in 2023, rising to 580 in 2024 amid wider concerns about the polluted state of the UK's waterways.

Despite this, the spot has been rated as "sufficient" by the Environment Agency, indicating that it meets the minimum standard required for UK bathing spots. But experts have warned swimmers to stay informed about the level of bacteria and pollutants in the water before jumping straight in, and called for higher standards and more frequent monitoring to mitigate the risk to the environment and public health. Professor Davey Jones, a soil and environmental scientist at Bangor University, said the bacteria found in water pose "one of the biggest threats to human health".

"Some pathogens, like E.coli 0157, can enter groundwater through agricultural run-off and pose serious health risks, even in small amounts," he told The Independent.

"As recreational water use increases, especially in urban settings like London, it's viral we broaden our testing frameworks to include viral contaminants."

Amelia Hornsby, from the Bathing Mobility Advisory Service (BMAS), who carried out the water analysis, added: "Consistently high standards [of water quality] are essential not only for protecting ecosystems, but also for ensuring safe and enjoyable access to our natural waters for local communities and visitors alike."

The Serpentine Lido wasn't the only wild swimming spot in London to see a spike in E.coli bacteria last year, with the BMAS also recording a 230% increase, from 100 to 310 in 2024.

Following criticism about the poor state of the country's waterways, and after figures showed that dozens of coasts, lakes and rivers failed to meet the minimum water quality standard last year, the government announced significant reforms to its Bathing Water Regulations in March.

The changes include an alteration of the legal definition of "bather", removing fixed bathing season dates for more flexible monitoring and improving the criteria used to assess future sites.