Unexploded ordnance (UXO) from the World Wars on the North Sea floor pose an uncertain occupational safety risk for dredging and cable installation. At present mitigation strategies are based on an interpretation of the precautionary principle that uses a worst-case approach, that is, assuming that UXO will be encountered, will explode, and will harm people onboard. We propose a probabilistic framework to estimate the UXO risk. Using this probabilistic framework, we conclude that the UXO risk during cable installation meets the prevailing safety standard in the Netherlands. Furthermore, we demonstrate that the UXO risk is lower than the general maritime risk, that is, the occupational health risk caused by the mitigation is higher than the UXO risk itself. We conclude that even for uncertain occupational risks, such as the UXO risk in the North Sea, a probabilistic analysis can be more instrumental in the decision-making process on accepting and mitigating risks than using worst-case scenario thinking.