Due to the non-physical junction between the power source and load, the undersea wireless power transfer (UWPT) system is suitable for charging small, submerged devices without a complex and costly sealing structure, plug-in cables and human interaction. For the shore-based power supply situation, the underwater power conversion and junction technology should be required to drop down shore-based voltage to the target voltage for the underwater energy supply of the UWPT system. This chapter proposes a lightweight, high power density, and high efficiency undersea power conversion connector system for the UWPT station, the LLC resonant converter circuit is built with a SiC power switching device. The full load range zero-voltage switching (ZVS) and load adaptive characteristics have been achieved. It adopts the optimized RC level shift driver structure to reduce the switching loss of SiC MOSFETs. The 1000 V shore-based voltage was converted to the 375 V target voltage for the UWPT station. The measured highest efficiency is over 98% at the load power level of 1500 W under the water condition.