The legacy of a Nazi submarine continues to “haunt” the waters of Europe.
In February 1945, just months before the Nazis were defeated, a German Navy U-boat was torpedoed down by the British Royal Navy in the waters off the Norwegian coast, killing all 73 of its crew. In a last-ditch attempt to supply their allies in Japan, the submarine was en route with a very important delivery: 65 to 70 tonnes of mercury.
Some 70 years on, U-864 still lies in the North Sea near the city of Bergen, even amid continued fears of highly toxic liquid mercury seeping out into the surrounding environment.
The wreckage of U-864 was found by the Norwegian Navy in March 2003. Not long after, the authorities came across documents that suggested the possibility of mercury on board. Mercury is naturally occurring and can be found throughout the environment, especially in seafood. Nevertheless, fears quickly spread that the U-boat's cargo could be making its way into the surrounding waters (based on North Sea fish) and potentially work its way up along the food chain to humans.

The Norwegian Food Safety Authority put a warning out to children and pregnant women to steer clear of seafood from the area, although that warning was eventually lifted in 2015 due to a lack of evidence. Nevertheless, researchers have continued to worry about the effects of U-864. A scientific study, published in the journal Chemosphere in 2011, argued that local Atlantic cod had elevated mercury levels in their liver and gills.
However, fixing the problem is no small feat. The wreck lies on a steeply inclined seabed made of unstable sediment. Any plan to move the wreck, therefore, could risk a landslide, which would be a double disaster if there are still live warheads onboard.

"We have to assume that there are still torpedos on board – at least a couple," Ane Eide Kjeras, a spokeswoman for the Norwegian Coastal Administration, told Der Spiegel in 2006. "There is a far higher risk of one exploding during a salvage operation."
The Norwegian government has recently proposed another controversial solution. The state budget in 2019 plans to set aside 30 million Norwegian Krone ($1.5 million) to essentially seal up the wreck under a thick “sarcophagus”. Although that plan is not yet official, they say it could be completed as early as the summer of 2020.