Fath is a chemistry professor in Furtwangen in southwestern Germany, and the action aims to highlight and control water quality in one of Europe's major rivers.
I'll swim all the way to the North Sea, and along the way, test the water for microplastics and other substances, he says according to the Czech news agency CTK.
The project began on Friday in the Czech Republic, where the Elbe's source is located. Over 25 days, the 59-year-old will swim through Czech cities like Usti and Decin, and then German Magdeburg and Hamburg before reaching the finish line in German Cuxhaven by the North Sea.
If he really succeeds in defying shipping traffic and tides, it means 44 kilometers of swimming every day – equivalent to more than a marathon. But on the other hand, he's moving with the current, so Fath is expected to be able to maintain a good pace without too much effort for large parts of the journey.
Fath is reported to be known as "the swimming professor" after similar previous actions in the Rhine, Tennessee River, and Danube.
According to the EU's water project Immerse, the Elbe was heavily polluted by human emissions until the early 1980s. In connection with Germany's reunification, an international cooperation was established to protect the river, abbreviated as Ikse, and now the water is supposed to be better.
