Between 1949 and 1982, several European countries, including the United Kingdom and France, submerged approximately 200,000 barrels of radioactive waste in a 14,500 km² area of the North-East Atlantic. At the time, the deep ocean was seen as a practical solution to dispose of materials that were difficult to manage on land. The waste, which included isotopes such as cobalt 60, niobium 94, cesium 137, and americium 241, was sealed in metal barrels and sunk to great depths, often more than 4,000 meters below the surface. No country has returned to monitor or retrieve these barrels since they were dumped, leaving the North-East Atlantic as a largely unmonitored nuclear waste site. The NODSSUM scientific campaign, conducted by the CNRS in 2025 using the autonomous robot Ulyx, aimed to investigate the condition of these submerged barrels. The expedition mapped less than 2% of the total area, covering about 165 square kilometers, and located more than 3,500 barrels. Some of the containers were found to be corroded and leaking, while others had remained intact. Interestingly, marine life such as corals, sponges, and crabs had colonized the barrels, transforming them into artificial reefs. Despite the presence of radioactive materials, no contamination was detected in the instruments used during the survey, suggesting that the waste has not yet posed an immediate threat to the surrounding environment. The decision to dump radioactive waste in the ocean was influenced by the limited infrastructure available for land-based storage at the time. The deep sea was perceived as a remote and isolated space, far from human populations and cities. The barrels were designed to contain the waste for about twenty years, a period intended to allow the most unstable radioactive elements to decay. However, the half-lives of many of these isotopes are much longer, sometimes exceeding centuries. This mismatch between the original expectations and the long-term reality of the waste has become a growing concern for scientists and environmentalists. The NODSSUM campaign has only scratched the surface of this underwater dump, revealing that the majority of the area remains largely unexplored. The scientists involved in the project emphasize that understanding the full extent of the issue will require significant time, resources, and political commitment. As the world continues to grapple with the long-term consequences of past decisions, the submerged barrels in the North-East Atlantic serve as a reminder that the choices made decades ago can still have lasting impacts. While the ocean has absorbed these remnants of the past, it is now up to current generations to determine whether this hidden legacy deserves the attention and action it requires.