A century-old German submarine, UC-30, has been found to be leaking TNT—trinitrotoluene, a powerful explosive—into the surrounding water, seabed, and marine life more than 100 years after it sank. Scientists are raising concerns that thousands of similar sunken ships and submarines, many from World War I and World War II, could be slowly leaking toxic materials as they corrode over time. The UC-30 sank in April 1917 when it struck a British mine while trying to return to Germany after experiencing engine failure. All 27 crew members died. The submarine remained lost until 2016, when it was discovered by Danish diver Gert Normann Andersen. Since then, it has been studied as part of the NorthSeaWrecks research project. Aarhus University professor Katrine Juul Andresen and her team, including navy divers, collected samples of water, sediment, and local marine life such as starfish and mussels. They also recorded video and photos to evaluate the condition of the wreck and the exposure of its mines. The study found that TNT from the UC-30 is entering the surrounding marine environment. Traces of the explosive were detected in the water, the seabed, and in the tissues of marine organisms. While the exact impact of this pollution is still unclear, the researchers believe the contamination is likely localized. However, as the wreck continues to corrode, more TNT could be released, worsening the environmental impact. The North Sea was a crucial battleground during World War I, with both Germany and Britain relying heavily on submarines and naval mines. An estimated 190,000 mines were laid in the area during the war, and the region was the site of the Battle of Jutland, the largest naval battle in history. Today, the legacy of these conflicts remains in the form of sunken ships and unexploded ordnance. In 2024, Andresen completed a report for the Danish Environmental Protection Agency, identifying 10,127 wrecks in Danish waters, with about 15% dating back to the World Wars. The report highlights the need for future action to address pollution from the most hazardous wrecks. Germany has invested in recovering some of these wrecks and World War II-era munitions from the Baltic Sea. However, removing explosives from the ocean is complex—detonating them underwater could spread contaminants even further. To address this challenge, Andresen is working with international researchers on the EU-funded REMARCO project. This initiative is exploring safer methods to manage submerged munitions, including using robots to map and monitor dangerous wrecks. While removing all hazardous materials from every wreck is not practical, new technologies may help reduce the environmental risks from the most vulnerable sites.