Anchoring is one of the frequent processes undertaken by the crew on-board ship. Improper anchoring has significant consequences, such as anchor dredging, which may pose serious risks to the ship crew, marine environment and commodities. This paper aims to present a robust approach combining bow-tie approach with SLIM (Success Likelihood Index Method) under fuzzy sets theory. Since the fuzzy bow-tie represents a comprehensive quantitative risk assessment (QRA) method, the SLIM predicts the probability of a human error occurring during a specific task's completion. In this context, anchor dredging risk can be calculated for a specific case. This paper's novelty lies in consideration of human error's contribution to risk for ship anchor dredging and combining quantitative and qualitative analysis in maritime risk assessment. The finding of the paper shows that the occurrence probability of anchor dredging risk for cargo ships is 7.31E-02. Besides its robust theoretical background, cargo ship owners, superintendents, safety inspectors, and health, safety, environment and quality (HSEQ) managers can utilise the paper's findings to minimise potential risk and enhance operational safety during anchoring operations.