The environmental risks associated to dumped munition, unexploded ordnance (UXO) and sunken war ships gaining more and more attention nowadays. Hundreds of wrecked ships and planes lie at the bottom of the North Sea alone, as well as thousands of tons of conventional and chemical munition. These warfare materials carry a significant risk of chemical leakage, posing a serve threat to marine wildlife. As part of the international EU project North Sea Wrecks (NSW), the present study aimed to assess the hazard potential of pollution by explosives on the marine fauna associated to sunken war ships loaded with munition and UXO. For this purpose, transplanted blue mussels (Mytilus edulis) were exposed for several month at two wrecks loaded with munition (HSM Basilisk and John Mahn) in order to detect leakage of explosives and to characterize the effects of those substances on mussel health. The hazardous potential was assessed using multi-biomarker analysis, which includes the enzyme activity of catalase (CAT), glutathione-S-transferase (GST) and acetylcholinesterase (AChE), as well as the histochemical biomarkers lipofuscin (LIPF), neutral lipids (NL) and glycogen (GLY). In addition, the condition index (CI) and the gonadal status were determined. Here, two cruises were conducted: One test cruise in 2019 to both wrecks, and a second in 2020 to the John Mahn, during which the main investigation took place. Chemical analysis of water samples, passive sampler, mussel tissue and sediments indicated leakage of explosives at both wrecks, as well as subsequent uptake by mussels and diffusion into the sediment. Detected chemical concentrations were in the range of a few nanograms. CI and gonad status indicated comparable mussel conditions between the stations. Biomarker results did not always correlate with increased explosive concentration or when exposed directly next to UXO’s. At most, moderate oxidative stress was detected using CAT and LIPF, but in general the low concentration of explosives and the short exposure time did not alter a biomarker response within mussels. In conclusion, the leakage of chemicals at the HSM Basilisk and the John Mahn was not high enough to endanger mussel health during the short-term experiment. It remains to be seen if the fish samples of the long-term experiment, which were also taken as part of the NSW project, will show more clear effects.