Hundreds of people on Tuesday jumped again into the Spree River's slow-moving, greenish water to show that it's not only clean enough, but also lots of fun to splash and swim in the Berlin's historic Mitte neighborhood along the world-famous Museum Island.

A group calling itself Fluss Bad Berlin, or River Pool Berlin, has been lobbying for several years to open up the river for swimmers again.

To circumvent the ban, the group registered their collective swim event as an official protest.

The group stresses that they want the people to use the Spree for recreation again, pointing out that the river has been cleaned up thoroughly, and that the water quality has improved in the last decade and is constantly being monitored.

Even city officials in the central Mitte district of Berlin say they would be interested in introducing river swimming again in 2026.

Supporters of lifting the swimming ban also point at Paris, where the Seine River was opened up for swimmers for the Olympic Games last year and will be opened this summer for Parisians.

Swimming there had been banned since 1923.

Only in Berlin, swimming has been continuously prohibited in the Spree since May 1925, when the German capital closed all traditional river pools because the water was deemed too toxic.

Some of those pools weren't only used for recreational swimming, but were a place for poor people to wash themselves if they didn't have bathrooms at home.

These days, the water is clean on most days, except when there's heavy rain, which leads to some water pollution.

Allowing swimmers to dive into the river would also mean loosening the historical monument protection on some parts of the river banks to install easy access ways to the water and places for life guards.

Another problem is the busy boat traffic on the Spree that could endanger swimmers.

However, for the time being, the Fluss Bad Berlin group only wants to open up the 1.8-km-long (1.1 mile) canal where there's no boat traffic.