The Danube has fallen to its lowest level for more than 120 years, paralysing shipping and at one stretch, between Serbia and Romania, revealing the wrecks of a long-forgotten fleet of World War II German warships.
You cannot mistake just how dramatically the Danube has dropped when you stand here on the quayside at the Serbian port of Prehovo.
The Germans were in fast retreat
A series of depth markers, some 10 metres in height, slips down towards the river only to run out before the surface of the water.
The harbour master jokes that for the first time in his career there is no point even trying to record the river's depth.
But his is the only joke along the banks of what is meant to be Europe's mightiest waterway.
Usually, at least a dozen so-called "convoys" of vessels - massive tugs pulling long lines of barges - plough their way between the Black Sea and the heart of the European continent.
The economic loss is incalculable. But there is another reason for the Danube's level to cause concern as well.
Just upstream of Prehovo, a tangle of metal shapes has broken through the rippling surface - the remnants of what was once Hitler's Danube Fleet.
The river was as strategically important then as it is now but when in 1944 the Nazi forces were in retreat, the German admirals felt they had only one option - to scuttle more than 80 of their river-going warships.
Now, all because of the drought that has afflicted great swathes of Europe this summer, this footnote in history has resurfaced.
The river authorities were amazed at this discovery and immediately began questioning local people for more information - with startling results.
One old man we spoke to, Vojislav Lapadatavic, who had worked in the German military kitchens, described how the ships were sunk even though there were wounded crewmen on board.
"We saw people on board a hospital ship one night and the next morning the ship had been sunk," he said.
According to local accounts, as many as 2,000 German sailors who were too badly wounded to be evacuated during the retreat by land would have perished in the operation.
The thought of so many men doomed in that way - even the enemy - still haunts those who work on the river.
A hazard to modern-day shipping
A local TV company hired divers to try to get a look underwater but to no avail - there was too much silt and mud for clear pictures.
Many people in Prehovo blame global warming for what is happening to the Danube.
They also wonder what other grim discoveries there may be before the waters rise again.