Beneath the bustling port of Saint-Nazaire on France’s Atlantic coast, remnants of World War II ordnance remain buried in the sediment, untouched and still potentially active. These unexploded bombs and shells were left behind when German forces surrendered in May 1945, and they are still a concern for construction workers and local authorities. Specialized teams in pyrotechnic decontamination are often called in to handle any disturbance, but the city has largely chosen to manage the risk rather than launch a full-scale cleanup. During the final days of the war, German troops deliberately buried vast amounts of ammunition in the port’s basins to prevent it from falling into Allied hands. The sediment covering these explosives has slowed their degradation by limiting exposure to oxygen, but natural processes and human activity—like dredging or construction—can still displace or expose them. A major cleanup has never been initiated due to the high costs, the risks involved, and the reluctance of local authorities to take on public responsibility for such a dangerous task. Saint-Nazaire was among the last French ports to be liberated. The city and its surrounding estuary were a key area of resistance for the Germans, known as the Saint-Nazaire pocket, until their surrender on May 11, 1945. The strategic importance of the port led to the accumulation of large amounts of military supplies, many of which were buried to prevent capture. Today, the city still bears the marks of this history, including a massive concrete submarine base built by the Germans in 1941, which remains a powerful reminder of the wartime occupation. Removing ordnance from the past is a complex and dangerous process. Over time, the metal may corrode, and the detonators can become more sensitive, making any handling a risk of accidental explosion. These are not just old, rusty objects—they are explosive devices whose condition is uncertain. The high cost of such operations, which require months of preparation, specialized teams, and significant funding, deters many local authorities from acting unless there is an immediate threat. While the sediment currently limits the risk by protecting the ordnance from oxygen and shocks, this protection is not permanent. Activities such as port construction, dredging, or even severe storms can disturb the buried explosives. Saint-Nazaire is not alone in this issue—other French ports along the Atlantic coast have also discovered remnants of wartime armaments during construction or dredging projects. These discoveries often involve British bombs or shells, highlighting the widespread nature of the problem. Across Europe, many major ports that were significant during World War II still contain similar remnants. These unexploded ordnances, often overlooked due to limited resources or political will, remain submerged along the French coastline. Occasionally, urgent or visible situations prompt underwater decontamination efforts. This issue reflects a broader challenge in managing wartime remnants in areas that are now crucial for economic activity, showing that Saint-Nazaire’s situation is part of a much larger, ongoing concern.