Imagine floating peacefully on one of the most beautiful rivers in the world, as the sun shines brightly above you and light glitters across the blue water.
You look up and – yes – that’s the Eiffel Tower completing a scene of utter delight, along with ancient golden bridges leading down to the Louvre and Notre-Dame cathedral.
Fishermen mix with bathers on green banks – there is not a car in sight – and the salmon, trout, eel and perch are all biting.
You might soon start to feel like you’re in an Impressionist painting – Le Pont Neuf, by Auguste Renoir, or an equally uplifting Monet.
No, this isn’t a preposterous dream. Paris city council has pretty much guaranteed that we will be swimming in the Seine by next year.
Dealing with lavatory waste, aeroplane fuel and fertiliser
In what sounds like one of the best possible legacies of the 2024 Olympics, almost €1.5billion has been poured into making the waterway swimmable.
Unlike previous claims – notably by the late Jacques Chirac when he was mayor of Paris from 1977 to 1995 – this one is based on science, rather than romantic myths.
You can dream about urban swimming for as long as you like – and Mr Chirac certainly did – but dealing with the disease-spreading bacteria such as e-coli that have infected the river for centuries has been an insurmountable problem.
Every kind of detritus has found its way into the river over the years, from lavatory waste to aeroplane fuel and fertiliser residue.
There were long periods of history when corpses were regularly dumped in, including plenty resulting from violent revolutions, wars and criminal activity.
Storm tank and purification systems
Now, an enormous subterranean tank is being completed beneath a public park close to Austerlitz station, on the Left Bank of the Seine.
It can hold as much water as 30 Olympic-size swimming pools – around 46,000 cubic metres-worth – and will have one primary job: to store runoff rainwater full of untreated waste.
Rather than allowing this deluge of filth to enter the Seine, as has happened up until now to stop it overwhelming the city’s sanitation network, it will remain in the tank.
As well as this storm tank, water purification is being achieved through a variety of measures, including reed beds that filter polluted rainwater.
There’s still the problem of the Seine’s bateaux mouches – the floating pleasure palaces used by tourists and partygoers – and other shipping, but this can easily be solved by fencing off designated swimming areas, as currently happens in busy harbours such as the one in Copenhagen.
Olympic Triathlon brought money
Bathing has been illegal in the Seine since 1923 (plenty of people have ignored the law, although less so as pollution intensified along with industrialisation), but this will all change.
In the short term, events such as the Olympic Triathlon will be held in the Seine before more than 20 marked basins – these will be the swimming pools – open for the public.
Efforts will be made to stop people diving off bridges or getting in the way of shipping.
It is also hoped that the old joke about why the French call their pools piscines – because they always ‘p*ss in’ them – might prompt better hygiene.
More seriously, Seine currents can be murderous – drownings are common – but no more so than off popular beaches, where teams of lifeguards are always on duty, just as they will be in Paris.
Why this has all taken so long can be explained with one word: money.
A greener Paris has cost a fortune in this case, and it’s thanks to the Olympics that the money was available.
For those who want to live a long-held dream, it is a price well worth paying.