In the sea, accidents as well as collisions caused by operating ships under the influence of alcohol can cause serious human and physical damage as well as marine environmental pollution. Despite the growing social and societal damage caused by such drunk driving, it is pointed out that under the current law, punishment is lighter than the gravity of the violation. In order to prevent the recurrence of such accidents, the actual conditions and case analysis of the operating vessels under the influence of Alcohol were conducted. Five participants with navigational skills and experience were volunteered, and carried out a standard manoeuvre using a computer-controlled vessel simulator, under three different blood alcohol concentrations (0.00%, 0.05%, 0.08% BAC). Results from the simulations were used to assess the performance and the decision making ability of participants under the influence of alcohol. In addition, the responses and behaviour of the simulated vessel when the navigators were intoxicated were analysed. Workload experienced by participants during the simulations were also assessed using the NASA Task Load Index. Based on the scenario results, a model for preventing drunken operation of ships is established and a plan to apply it is proposed. In addition, in order to effectively strengthen the measures against operating vessels under the influence of alcohol, efforts should be made to reduce accidents that are caused due to intoxication, and operating vessels under the influence of alcohol through strengthening relevant laws and, strengthening special or occasional examinations conducted by the police officers of Korea Coast Guard in ports.