Thames River swim challenge interrupted by high pollution levels in Henley

A group of world-class swimmers who swam the Thames this week to raise awareness of river pollution had their challenge interrupted by high levels of e-coli due to raw sewage on Wednesday in Henley.

Eight swimmers, who included Olympians and athletes from all four of the UK nations, set off on Monday from Lechlade to swim 200km in relay along the Thames and arrived in Teddington Lock on Thursday. The swim was organised by Surfers Against Sewage exposing the limits of a broken water system and demanding urgent action to end sewage pollution.

In Henley, known for its hotspot for sewage pollution, the data was so concerning that the swimmers briefly hopped into the boat. Readings immediately after Henley showed E. coli levels at 150 times higher than the stretch before Marsh Lock.

A spokesperson for Surfers Against Sewage said, “During the swim, samples were collected and live data shared from the Thames using a Seneye water quality sensor, giving real-time water quality readings every 15 minutes. This data didn’t just track the swimmers it exposed the truth about our rivers in the moment.”

Laura Reineke from Friends of the Thames said, “This is a wake up call, and epitomises what this swim is protesting. If you’re a Henley resident, this should leave you outraged, frustrated, and embarrassed by the state of our water – come along and cheer on the team looking to protest our water mismanagement and bring about change for our waterways!”

Toby Robinson, who competed in the 2024 Paris Olympics, estimated the team had been forced to skip about 15 kilometres of their route because of pollution concerns. He said, “As we got closer to London there’s just much more debris in the water and I’ve been bumping into a lot more stuff,” he said. “The water changes colour. Towards the source it was greenish, but further down it’s changed to a more browny colour.”

Thames Water was fined a record £122.7 million in May 2025 by the industry regulator Ofwat for failing to maintain its sewage systems and for paying undue dividends to shareholders.

Photo credit: Surfers Against Sewage