May the best team ... not get violently ill.

British boaters are being warned of alarmingly high levels of E. coli from sewage in the River Thames in London ahead of the historic Gemini Boat Race between Oxford and Cambridge universities on March 30.

The environmental group River Action said regular testing along the race course between Feb. 28 and March 26 showed E. coli levels up to 10 times higher than what the U.K.'s Environment Agency allows for designated bathing waters graded "poor," the lowest of four categories. The government advises against bathing in waters graded poor.

"The testing locations suggest that the source of pollution is from Thames Water discharging sewage directly into the river and its tributaries," River Action said.

Thames Water, a regional utility, has long faced controversy over pollution, but told the Financial Thames that heavy rains are responsible for the water quality readings reported by River Action.

"We are in a tragic situation when elite athletes are issued with health guidance ahead of a historic race on the capital's river. Our water quality results show what happens after decades of neglect by an unregulated water company, Thames Water," said River Action CEO James Wallace.

"Recently we heard from Thames Water how they will not contribute to a £180 million ($227.2 million) industry-wide scheme to fast-track efforts to reduce pollution in England's waterways. But they do want to increase customer bills and increase dividends to shareholders as well as position to get a massive taxpayer bailout to clear debts including a £190 million ($239.8 million) loan due in April," said river champion and naturalist Steve Backshall MBE.

"From where I am standing, Thames Water is one flush from disappearing down its broken sewage pipe."

The Environmental Agency on Tuesday opened a portal for water company whistleblowers to safely report serious environmental wrongdoing. The move comes as the agency is conducting "the largest ever criminal investigation into potential widespread non-compliance by water and sewerage companies at thousands of sewage treatment works."

"The more evidence we have to identify potential criminality, then the more actions we can take to make lasting improvements to our environment," said Alan Lovell, Chair of the Environment Agency.

River Action said it worked with The Rivers Trust and British Rowing to develop guidelines for boater safety in poor quality water, and those guidelines were issued to rowing clubs across the country to minimize the risk of illness. The guidelines were also included in the briefing packs for Oxford and Cambridge rowers participating in the Gemini Boat Race this weekend.

The recommendations include covering cuts, grazes, and blisters with waterproof dressings; taking care not to swallow river water that splashes close to the mouth; wearing suitable footwear when launching or recovering a boat; and cleaning all equipment thoroughly.

"As a rower, the water I row on is my field of play, and the results of the E.coli testing show that rowers are putting their health at risk to do the sport they love. Thousands of people rely on our rivers for work and recreation, and they are being choked with sewage and pollution," said Imogen Grant, triple Boat Race winner with Cambridge, double World and European champion rower.

"Over 30 rowing clubs sit along the Boat Race course, with thousands of rowers taking to the Thames every day," said British Rowing CEO Alastair Marks.

"Our recently launched Environmental Sustainability Strategy outlines the steps rowers can take to row safely, so we can keep rowing and keep inspiring a love and care for our waters in our community."

The Oxford-Cambridge Boat Race has been held annually since 1829. The 2024 Gemini Boat Race will be the 169th men's race and the 78th women's race, drawing hundreds of thousands of spectators to the banks of the River Thames.

— with reporting by TMX