This paper proposes an undersea simultaneous wireless power and data transfer (SWPDT) system with full-duplex mode based on shared channel. The shared channel is composed of a coupler that including an overlapping direct-quadrature (D-Q) transmitter and a dipole receiver. The two layers transmitting windings are decoupled, and which can form a amplitude-constant traveling magnetic wave under the spatiotemporal coordination mechanism, thereby suppressing output fluctuation with misalignments. Besides, the system adopts a bilateral LCC compensation topology with blocking network, creating create favorable conditions for data transfer. To achieve the full-duplex mode, the frequency division multiplexing (FDM) is utilized. The signal is modulated by frequency shift keying (FSK) method, and the power transmission frequency is set to 85 kHz. By using FSK modulation, communication bands of signal transmission are set to 1.2 MHz and 2 MHz, respectively. Finally, the simulation results verify the theoretical analysis and the efficient synchronous transmission of power and data in full duplex mode under the same channel are realized. The proposal achieves stable simultaneous wireless power and data transmission within a rotational misalignment range of [−30°, 30°] and an axial misalignment range of [−30 mm, 30 mm].