The Seine River has long been a beautiful backdrop in Paris but not the best place to swim.

Since 1923, swimming has been banned in the river, due to industrial waste and high levels of e.coli.

This is set to change as Paris prepares to host the Olympic Games in 2024. Officials want the water to be so safe they could hold two swimming contests in the river.

Today, the water doesn’t look particularly inviting but if you were tempted to take a dip you would face a fine. Public authorities hope a €1.4 billion (NZ$2.5 billion) plan can change this.

Samuel Colin-Canivez, Paris’ head engineer for swage projects, told the New York Times the goal was not to “purify” the Seine. Instead, they aimed to prevent untreated water from entering the river.

One way of doing this will be a massive retention pond, which will hold swage water during periods of heavy rain and then direct it towards a purification station.

This would help the river meet sanitary standards, which are set by a European directive.

Turning around the quality of a river as massive as the Seine seems like a big job, but hydrologist and Professor at Sorbonne University, Jean-Marie Mouchel, told Euro News he felt it was possible.

Mouchel said the river’s low flow and a small number of inhabitants made it possible to reduce the quantity of faecal bacteria in time.

“There are things going to be done and there are also some chemical products,” he said.

The professor added that efforts to improve the water quality had been made since the 1970s, so it was already at a “breathable state”.

If the new plan is successful, Paris City Hall intends on lifting the swimming ban and allowing the public into the river in 2025. As for how boats and swimmers could both safely use the waterway, discussions are under way.

Due to the impact rain can have, there is not a 100 per cent guarantee the river could be used for the Olympics, as a massive rainstorm just ahead of the Games could ruin efforts.