###### Abstract
[PERSON] (2019) proposed a flow-based VF-RRT\({}^{\star}\) method that optimizes USV navigation in ocean currents. This approach used upstream coefficients, biased sampling, and tree pruning to generate smoother, quicker paths in dynamic oceanic environments. [PERSON] (2019) proposed a customized fluid-guided incremental path planning method for USVs. This method thoroughly considers the dynamic factors of USVs, incorporating vortices and strictly adhering to international collision avoidance regulations. It effectively addresses the challenges posed by multiple dynamic obstacles in maritime traffic. However, while the streamline-based approach provides a smooth sailing path for USVs based on the principles of hydrodynamics, improvements are still needed in dealing with complex Marine environments. Existing route planning algorithms often ignore the marine environment's complex features and potential hazard factors, which are crucial considerations in route design to avoid risks such as ship grounding or collision. Safe water depths and minimum draft requirements are critical in shipping and waterborne construction, and ensuring adequate water depths for ships during navigation and berthing can significantly reduce the risk of grounding, thus protecting the ship's safety ([PERSON], 2018; [PERSON] et al., 2019; [PERSON] et al., 2019). [PERSON] (2019) proposed a modeling technique based on Delaunay triangulation to calculate safe water depths for ship navigation. This model also takes into account the size of the ship and tidal heights and uses [PERSON]'s algorithm to solve the adjusted network for adaptive path design. [PERSON] (2019) proposed a method that determines whether to activate surface or aerial navigation mode based on the current water depths. Setting a water depth reward function to control the timing of aerial flight and surface navigation ensures the safe operation of amphibus USVs in various environments, effectively avoiding risks. In addition to high-precision bathymetric data for enhanced accuracy and adaptability, it is crucial to consider USV characteristics and wave height factors to ensure vessels can safely navigate complex hydrographic conditions. The current study did not adequately consider the complex interaction of these factors. In summary, the study of USV path planning in complex seas is still challenging and requires further research. In path planning studies, current methods often overlook marine environment characteristics and potential hazards, leading to planning outcomesthat are less accurate and comprehensive. Many existing algorithms prioritize minimizing path length or energy consumption alone as evaluation criteria, neglecting navigation safety concerns. This oversight can cause planned routes to veer dangerously close to the boundaries of non-navigable areas, thereby heightening the risk of collisions. In this study, we propose a method that significantly enhances the navigation safety and efficiency of USVs in complex maritime environments. The main contributions are as follows. 1. To enhance the navigation safety of USVs in complex maritime environments such as densely islanded areas and shallow waters minimum safe water depths have been established in this study. 2. This study employs CFD technology to determine globally feasible paths for USVs, avoiding local optima. For complex maritime regions and areas with unknown hazards, we identified and marked potential dangers, using the improved A* algorithm for local path planning. This approach ensures a more comprehensive and practical global planning strategy.