To achieve intelligent monitoring and forecasting of the marine environment, we have developed a preliminary version of a digital twin of the ocean in Xiamen Bay. Based on the observation system and high-resolution numerical simulation, we construct the data base of this DTO. This system integrates comprehensive simulating and forecasting capabilities for hydrology, water quality, and ecology within Xiamen Bay, with a robust human-computer interaction interface alongside a state-of-the-art visualization system. Through different modules, the system will be able to provide disaster prevention and reduction services such as storm surge overtopping, social services such as garbage drift monitoring and forecasting, and economic services such as port terminal operation. The system also integrates an AI model to realize the functions of autonomous analysis and automatic generation of emergency plans, providing a decision-making management basis.