In underwater mobile visible light communication systems, the received optical power varies significantly when the transmission distance changes due to the large intrinsic absorption of water. This paper proposes an underwater mobile visible light communication technology based on Gain Feedback Control (GFC), which expands the dynamic range of both communication distance and Field of View (FOV). At a moving speed of 0.13 m/s, we achieved real-time duplex video transmission with adjustable communication distances between 0.9~5.2 m, data rates of 5.0 Mbit/s, video pixels of 800×600, and Frames Per Second (FPS) greater than zero. Compared with the system without GFC, the dynamic range of communication distance and receiving FOV angle has expanded to 5.3 and 2.8 times, respectively. In order to further verify the performance of the system, we measured the average scintillation index, data transmission outage probability, and Bit Error Rate (BER) of the system at different moving speeds. Within the dynamic range of communication distance, as the moving speed increases, the average scintillation index and BER correspondingly increase. However, even when the moving speed reaches 0.83 m/s, which is the maximum speed of the system, communication remains uninterrupted. Our results indicate that the system has good robustness and has good potential underwater mobile communication applications.