Wireless Power Transfer (WPT) effectively solves the problems of corrosion and leakage in underwater environments using the traditional plug-and-play charging method. In this paper, an underwater simultaneous wireless power and information transmission system based on magnetic induction coupling is investigated. Based on the combination of double-sided LCC compensation topology and wave-blocking network, four basic topologies of signal transmission are modeled, and then the signal transmission voltage gain and the influence of the energy channel on the signal channel under the four topologies are analyzed. Furthermore, the advantages and disadvantages of the simulation effects of the four topologies are compared, so as to validate the feasibility and correctness of the performance of the simultaneous wireless power and information transmission system and realize full-duplex signal transmission.