<p>The underwater wireless sensors (UWSs) play an important role in marine resource exploration. An autonomous underwater vehicle (AUV), which receives energy from an underwater docking station, is used for charging the UWSs. Therefore, a bidirectional underwater inductive wireless power transfer (BUIWPT) converter is often adopted by the AUV. However, the BUIWPT converter receives higher charging power from the underwater docking station, while it provides lower discharging power to the UWSs. Therefore, a variable-structure BUIWPT (VS-BUIWPT) converter is proposed. The proposed converter not only achieves different power transmission in both charging and discharging modes, but also maintains high transmission efficiency of the system, which is achieved by using a dual-SS compensation network, two different operating frequency, and variable compensation capacitors. Compared to the conventional phase-shift control and the addition of a dc-dc converter on the primary or secondary sides, variable frequency control reduces the complexity of the control, and because the compensation network is a dual-SS-type compensation network, the control process is not invalidated by frequency bifurcation. The system mathematical model is presented. Finally, simulation and experimental results confirm the theoretical analysis.</p>