Holding hands, people jumped in the water, and floated around in Boston's Charles River recently. That is something that would not have been possible years ago because the river was so polluted.

In the 1960s, the music group The Standells even sang about the river in their popular song, "Dirty Water."

"Well I love that Dirty Water, oh, Boston you're my home."

The swimmers were getting their once-a-year chance to cool off from the summer heat in the Charles River.

It is called "City Splash." For a few days each year, the state of Massachusetts allows public swimming on Boston's part of the nearly 130-kilometer river.

The event is in its fifth year. It is a chance for the nonprofit Charles River Conservancy to show its efforts to build a "swim park." Their idea is to build floating docks where swimmers can jump safely into the river— without touching the hazardous bottom. These docks would be in areas where the water quality would be tested repeatedly.

Nearly 300 people signed up to swim.

"It felt refreshing and wonderful,'' said Newton, Massachusetts resident Ira Hart as he got out of the river. "They used to talk about how it was toxic sludge and you'd glow if you came out of the Charles. Well I'm not glowing, at least not yet.''

Boston is one of the cities hoping to follow the model of Copenhagen, Denmark. That city opened the first of its three floating harbor baths in the early 2000s. On sunny days, people swim in the harbor baths surrounded by tall buildings and cars on the highways. At night, the area is filled with people enjoying music and food.

Just recently Paris opened public swimming in a once-polluted canal. New York, London, Berlin and other cities are planning similar features for their waterways.

In Boston, the Charles River Conservancy still needs to raise several million dollars. It also needs to get approvals from city, state and federal agencies.

The group's spokeswoman, S.J. Port, said the biggest problem has already been taken care of: The Charles is now one of the cleanest city rivers in America.

The U.S. Environmental Protection Agency announced this month that the river earned a "B" grade for water quality last year-- an "A" being the best grade. It means the Charles River met the requirement for swimming 55 percent of the time.

Here are examples of other cities working to allow swimming again:

Portland, Oregon

In Portland, Oregon, the city and a local group invited residents to swim in the Willamette River this summer.

They opened the first official public beach with lifeguards on the river earlier this month. They have also launched a public information campaign and scheduled events around the water.

Among them was the Big Float river parade on July 15. People floated on the river in inner tubes and small boats. About 2,500 people participated in the party.

London

In London, a group of architects, designers and engineers have plans for a series of pools in the middle of the River Thames. It would be in an area where river water would be filtered, or cleaned, continuously.
Chris Romer-Lee, a lead organizer of the Thames Baths project, said the group aims to submit plans to local authorities by early 2018.
The group launched an online funding campaign last year that raised about $180,000 to work on their design. Now they are working to raise almost $20 million for the project itself.

New York

In New York, four local artists and architects launched the idea for +Pool, a floating pool in the shape of a plus sign in 2010. The water would also be cleaned or filtered.

Since then, they say they have successfully tested a filtration system that removes bacteria without using chemicals.The group's deputy director said they have raised nearly $2 million to keep developing the project. They are exploring possible places on the East and Hudson rivers and are preparing to get city approvals.

Melbourne, Australia

In Melbourne, Australia, the Yarra Swim Co. presented its idea for a floating pool on the city's Yarra River at a show last year.

Michael O'Neill is behind the effort. He said the company will reach out to community groups and government agencies in August. They want to know what people think the Yarra Pools project should offer. They also want to support other ideas for use of the river.

Berlin

In Berlin, the Flussbad project calls for cleaning up a canal off the German capital's Spree River for public bathing.

Barbara Schindler is a spokeswoman for the effort. She said the idea has been around since the 1990s, but has made progress in recent years.
She said the organization completed a water quality study in 2015. It has received $4.6 million in government funding to hopefully create the project.

I'm Anne Ball.

And I'm Jonathan Evans.


Anne Ball adapted this story for Learning English from the Associated Press. Hai Do was the editor.