To address the problems of large sampling errors, low efficiency, sample contamination, and poor system stability in conventional water sampling technologies, a fully automated water sampling robot was developed. The robot was consisted of a hull frame, a multi-depth sampling module, an automatic bottle filling and sealing module, a bottle storage module, and a power module. The multi-depth sampling module employed a reel-based hose deployment mechanism, a 360° rotary joint, and electromagnetic directional valves to achieve continuous multi-depth sampling and pipeline self-cleaning. The filling and sealing module utilized an impeller-driven transmission assembly as a unified power source to accomplish bottle filling, capping, and bottle switching through mechanical linkage, thereby reducing contamination risk. A four-motor vector propulsion system was adopted to improve maneuverability, while a depth sensor combined with a fuzzy PID closed-loop control algorithm enabled real-time depth regulation. Ansys was used to perform static structural analysis on the hull frame and vector steering shaft, as well as a fluid-structure coupling analysis on the impeller to verify structural strength. The results show that the maximum stress and deformation of the hull frame are 3.22×10⁷ Pa and 0.030 mm, respectively, while those of the vector steering shaft are 3.81×10⁶ Pa and 0.13×10-3 mm. At a flow velocity of 15 m/s, the impeller exhibits a maximum stress of 4.77×10⁷ Pa and a maximum deformation of 0.031 mm, with a safety factor of 5.8. All components satisfy the strength requirements. The proposed robot integrates automation, mechanical linkage, and closed-loop control, effectively improving sampling efficiency and reliability and providing a technical reference for water environment monitoring in complex aquatic environments.