Thousands old, defective or outdated ammunition they have been for decades at the bottom of the idyllic lakes of Switzerland.

After World War I and for years after World War II – in between 1918 and 1964 – the Swiss were throwing the ammunition they didn’t need into the country’s lakes.

Now the authorities have started a competition of ideas on how they could “clean up” them bottoms from the old munitions, found between 150 and 220 meters deep in a number of lakes including Thun, Brienz and Lake Lucerne (centre photo).

“With the launch of an ideas competition, Armasuisse wants to increasingly involve academia and industry in the issue of a future, environmentally friendly and safe recovery of munitions from the depths of lakes,” the relevant announcement reads.

The three best entries will share one prize worth 50,000 Swiss francs ($57,800), according to a statement from the country’s federal defense procurement office (Armasuisse) published earlier this month.

Why haven’t they been withdrawn to date?

According to Armasuisse, a 2005 assessment of possible munitions recovery methods showed that “all proposed solutions available at the time would have resulted in massive mud turbulence and high risks to the fragile ecosystems of the munitions”.

The challenges to be considered for current ideas are poor visibility in lakes, the risk of munitions exploding, water depth, currents and the condition, size and weight of munitions, some weighing up to 50kg .

A further complication is the fact that some components are made of non-magnetic copper, brass or aluminium, according to Armasuisse.

“All of these factors represent major challenges for munitions recovery, using environmentally friendly methods,” the statement added.

The contest is open until February 6, 2025, with winners scheduled to be announced in April.