The Swiss Air Force used Lake Neuchâtel for bombing exercises until 2021.

There are about 4,500 tons of ammunition in the lake, some of it in waters only 20 feet deep.

Most of the deadly weapons sunk in other lakes can be found at depths of up to 213 meters.

An estimated 3,300 tons of weapons are stored in Lake Lucerne, the BBC reported, and even more are in Lake Thun and Lake Brienz.

Marcos Buser, a retired geologist, wrote a research paper ten years ago warning about the garbage dumps.

He said there was still a risk of the ammunition exploding because in many cases “the army did not remove the detonators before dropping the ammunition.”

The submerged ammunition is sometimes covered with sediment up to 1.80 m thick. If this is stirred up during recovery, it can lead to a decrease in the oxygen level under water.

Previous plans to recover the munitions were scrapped due to the risk of “massive mud turbulence” that could disrupt sensitive ecosystems.

At the time, geologists had advised the army to dispose of the ammunition it no longer needed safely. However, the army has now turned to the public for new ideas.

It is a legacy of the Swiss defense strategy of “armed neutrality” – maintaining a large army with conscription for all men.

The deadline for submitting solutions is February next year.

The plans will be judged by an anonymous jury of experts and the three winners will be announced next April and will share the prize money.

“There are no plans to immediately implement the submitted proposals, but they could serve as a basis for further clarifications or the initiation of research projects,” the Defense Ministry said.