When Sweden scuttled 20 huge wooden warships more than 250 years ago, it was seen as a desperate measure to block the enemy Danish fleet.
Now those same wrecks could scuttle the key component of a European energy plan - the construction of a 1,200km (746-mile) gas pipeline along the cluttered floor of the Baltic Sea.
Russia and Germany are building the pipeline to avoid the political problems of transporting gas overland - Ukraine and Belarus, in the midst of price rows with the energy supplier Gazprom, have threatened to interrupt supplies to Western Europe.
The seabed route, known as Nord Stream, is turning into an obstacle course of a different kind.
Not only do 100,000 tonnes of unexploded Nord Stream ammunitions lie scattered along the route, but the German Navy is concerned that one of its live shells might hit the pipeline and set off an explosion during Baltic exercises.