Ocean energy is one of the renewable energy sources. Ocean thermal energy is the most abundant in marine energy, so it has a good development prospect. At present, the main way to use ocean energy is power generation. However, it has disadvantages: low efficiency and high energy consumption. In view of the above shortcomings, this study puts forward a new type of ocean energy comprehensive utilisation system of water–electricity cogeneration. The system is based on the ocean thermal energy conversion: wave energy power generation and solar pond are integrated in the system. The basic principle and working process were analysed, and the energy consumption and the product of the system were calculated. As shown in the calculation results, it is effective to reduce energy consumption and improve the system efficiency. The research of this study has valuable reference for the development of ocean energy in the future.