Ocean and marine environments face the adverse effects of climate change and environmental pollution. Maritime transportation, one of the most severe marine pollution sources because of ship-sourced operations, poses risks to the marine environment in many types and ways. A robust risk assessment should be organised to identify causal mechanisms and the resources of the pollution. In this study, the steps of ship operations that may cause marine pollution and the structure of the relations between them were established based on their expert opinions and the information contained in the literature. On this basis, the probabilities of each ship's operations that cause marine pollution are computed by the Fuzzy Bayesian Network approach. The extent of the response operation according to the level of marine pollution is determined by the Bow-tie approach. As a result, the procedures that cause funnel gas emissions are the riskiest. The study will be beneficial for the practitioners of safety and environmental management in maritime transportation to make decisions practically and strategically.