This book constructs a complete knowledge framework of undersea wireless power transfer technology, following the main thread of “fundamental theories-key technologies-application scenarios-future challenges”. In the section on fundamental theories, authors delve into the characteristics of electromagnetic wave propagation in seawater media, magnetic coupling resonance mechanisms, electric field coupling mechanisms, and energy-information co-transmission models. The chapter on key technologies focuses on core issues such as high-frequency inverter design, adaptive impedance matching, multi-objective optimization algorithms, and pressure—and corrosion-resistant materials. The section on application scenarios combines practical cases from deep-sea exploration, underwater Internet of Things (IoT), and military equipment to analyze the engineering challenges faced in implementing these technologies. Additionally, this book features a special chapter on “Interdisciplinary Integration,” highlighting the importance of cross-domain innovation involving ocean engineering, power electronics, mechanical engineering, materials science, and artificial intelligence within this field.