PARIS - The event was supposed to start on September 2 at 7 a.m. at the Josephine Baker swimming pool in Paris, on the banks of the Seine River. More than 3000 participants had signed up to take part in the swim that would take them up the Seine to the André-Citroën Park, west of the city.

But a few days before the race, Paris’ Prefecture of Police suddenly cancelled the event. “There is something quite brutal about this decision, and its reasons are unclear,” laments Laurent Neuville from Paris Swim, the race’s organizer. “Our idea was to reinstate an event that was very popular at the beginning of the 20th century; we had been working on it since December 2011. There are thousands of similar races in London, Amsterdam, New York… Swimming down a river like the Seine, which has many access points leading to its banks, is safer than swimming across the Bosphorus, isn’t it?”

The Police Prefecture claims to have held several “inter-service meetings” before making its decision. The navigation on the Seine River -- which would have been affected during four days -- was one of the main issues. The Prefecture then turned towards the Regional Health Agency (ARS). The agency judged the event too risky for the health of the participants, stating that the quality of the water was still too low for swimming, despite recent improvements. If the Prefecture let the Paris triathlon take place in July, it was only because it had not received the ARS notice in time.

The event organizers tested the water underneath Bir Hakeim Bridge on August 9 and showed the Prefecture their results -- which were in line with sanitary standards -- but the Prefecture wouldn’t budge. Will we ever be able to take a swim in the Seine River? The Prefecture’s answer is “no” and says their refusal is a “a principled position” that will apply to all similar requests.

This shows how polluted the water must be. How bad is it by the way? Don’t expect the ARS to tell you: while taking a swim in the river is forbidden in Paris, the Seine River’s water quality is not as closely monitored as France’s most touristic rivers, like the Dordogne or the Lot in southwestern France. And since the Seine’s water is never tested … swimming is very likely to remain forbidden.