This work envisions and shows the scenario of a low-carbon city at sea built by human beings to overcome the harsh environment of covering land due to rising seawater.In the future, all energy sources in the city will be low-carbon energy, and human beings will establish low-carbon energy centers and low-load energy systems within the low-carbon energy centers to ensure efficient use of energy.The city layout uses a central layout, dividing areas from the low-carbon energy center in all directions, with each area operating under the drive of a low-load energy system.At the same time, this work introduces several future technology concepts, which are floating base, energy floating board and super high-speed tunnel. Finally, with the continuous efforts of human beings, people live a happy and joyful life.