The submersible waterjet propeller (SMWJP) is more efficient than conventional stern waterjet propulsion, while its thrust will be significantly reduced during high-speed maneuvering. The working process of SMWJP in high-speed yaw maneuvering was simulated under a set of stationary oblique flow conditions. Compared with straight flow, the head and efficiency of SMWJP decreased by 20% and 17.6% for oblique flow with positive oblique flow angle, and by 40% and 23.5% for that with negative oblique flow angle. Based on the entropy generation theory used to evaluate flow loss, the distribution law of entropy generation for each component of SMWJP in oblique flow was derived. Turbulent dissipative entropy generation accounts for the largest proportion of total entropy generation, reaching 60%. And entropy generation in impeller flow passages accounts for 45% of the total. The entropy generation in the inlet duct accounts for the smallest proportion, while it was more easily affected by the oblique flow angle. The oblique flow leads to the formation of low-energy vortices in the inlet tube, which invades the impeller flow channel, resulting in the expansion of the high-entropy generation area on the front edge of the suction and the top of the leaf. The turbulent dissipative entropy generation was then increased. Therefore optimizing the design of the inlet tube and reducing the sensitivity of the inlet tube to oblique flow is the key way to improve the dynamic performance of the submersible propeller.