A submarine that sank in 1917 is still leaking TNT

In April 1917 a German submarine called UC-30 was moving past the Danish island of Rømø. It hit a British mine and sank with all 27 men on board. It had 18 mines and six torpedoes with it. Nobody knew where the wreck was until a Danish diver found it in 2016.

Researchers from Aarhus University have now taken samples from it. They worked with navy divers as part of a project called NorthSeaWrecks. They took water from around the wreck, sediment from the seabed, and animals living on the hull. TNT showed up in all three. The work was published in Marine Pollution Bulletin.

They also did one thing I thought was clever. They put blue mussels in cages, set them right on the wrecks, and left them there for weeks. Then they checked what had happened to the animals. The mussels were under real biological stress: cell damage, disrupted metabolism, drained energy reserves. So the mussels are not just proof that something leaked. They work as a measuring instrument.

The part that stuck with me is the scale of this. Danish waters alone have more than 10,000 known wrecks, and about 15 percent of them are from the two world wars. Steel corrodes at its own pace, and a lot of those hulls are getting to the point where whatever is sealed inside stops being sealed.

Nobody is going to raise them all. But a cheap test that tells you which ones are leaking right now seems like a reasonable place to start.

Source: https://www.sciencedaily.com/releases/2026/09/260913081919.htm