© Carlo Stanga, 2022. Courtesy of Flussbad Berlin e.V. Last June, a group that has spent years lobbying for the legalisation of swimming in parts of the Spree invited Berliners to take a dip in a section of canal along Museum Island, just beneath the Berliner Dom. The floating protest was intended to prove that the waters of Berlin’s central river are clean enough to be used not just for lethargic tourist boats, but public recreation, too.