## 4 Results and Discussion
### Community Detection
(1) When there are potential risks in the current environment, the relevant shore-based maritime authorities do not provide timely and accurate navigational guidance and poor ship-shore communication, resulting in the loss of seafarers' situational awareness, meanwhile seafarers fail to make full use of navigational aids and maintain a proper lookout, thus failing to make a full evaluation of the current dangerous situation, thus causing the subsequent series of seafarers' unsafe acts (U24, U25, U26, U27); (2) Due to the irregularity of the company's operation rules and regulations, the seafarers do not keep the vigilance required by the special situation in the complex navigation environment or the busy traffic, and fail to establish effective cooperation and communication between ships and within the bridge team, which cause the seafarers to lose situational awareness of the current environment, distracts their attention, and failure to keep a regular lookout, thus, leading to the subsequent series of seafarers' unsafe acts (U31, U24, U25, U26, U27); (3) The seafarers do not keep the AIS and other navigational aids in working condition, and do not follow the safety rules in restricted visibility, as well as the seafarers lose their situational awareness and do not maintain a proper lookout, so that they fail to make a full evaluation of the current dangerous situation, which leads to a subsequent series of seafarers' unsafe acts (U16, U24, U25, U26). Figure 11: Schematic diagram of seafarers’ unsafe act risk interaction community 1. Community 3 includes 4 nodes of tidal current effects (E7), external management (E8), failure to control the ship position (U18), and failure to determine the impact of environment on ship maneuvering (U30). The community involves two risk propagation paths of seafarers' unsafe acts, and has typical contact accident characteristics, as shown in Figure 13. The colored arrows refer to typical risk propagation paths. (1) The current water is in high tide/low tide situation, the seafarers fail to fully evaluate the effect of current environment on ship maneuvering, and fail to control the ship's position during the process of leaving berth, resulting in ship contact accidents; (2) Due to the defects in the management of external organizations such as wharf companies, the seafarers fail to fully evaluate the effect of the current environment on ship maneuvering and fail to control the ship's position under the effect of tidal currents, resulting in ship contact accidents. Community 4 includes 13 nodes such as insufficient device (O1), lack of operation certificate (O2), insufficient education and training (O3), and insufficient manning (O4). The community involves three risk propagation paths of seafarers' unsafe acts, as shown in Figure 14. The colored arrows refer to typical risk propagation paths. (1) Insufficient device preparation of the ship, such as the lack of paper charts and charts not updated in time, leads to the omission of the seafarers in designing the route plan, which makes the route plan with potential danger, meanwhile, due to the insufficient safety education and training received by the seafarers, the lack of implementation of the safety management system on board ship and the lack of supervision and guidance, the captain does not strictly review the route plan, which tends to cause the seafarers' unsafe acts, resulting in ship grounding accidents; (2) The ship is a inland ship, the seafarers on board have not been trained for sea navigation, the safety management system of the ship company has not been implemented on board. There is a lack of supervision and guidance, and the  
Figure 12: Schematic diagram of seafarers’ unsafe act risk interaction community 2. Figure 13: Schematic diagram of seafarers’ unsafe act risk interaction community 3.  
supervisors ignore the relevant regulations, which makes the inland ship navigate beyond the approved navigation area.