Visible light communication (VLC) offers a unique advantage of electromagnetic interference immunity and wide bandwidth. It has gradually become the main candidate in marine communication with great potential. As a green communication link, VLC requires reliable beam tracking as a prerequisite. Therefore, based on the received signal strength of a single-input-multiple-output system in the VLC scenario, this paper first proposes a geometrical algorithm for transmitter localization. On this basis, a linear iterative algorithm using Taylor expansion, implicit function theorem, and time-domain expansion is presented to realize online beam tracking. Under the marine VLC system, an iterative denoising algorithm based on the hidden Markov model and principal component analysis is proposed for denoising. Simulation results show that the proposed algorithms have predominance in high tracking accuracy (within 10 cm) and desirable real-time performance.