In the upcoming area of 6G, integrating sensing and communication in complex environments, such as satellites-denied sea surface, evolving into a key point for unmanned surface vehicle(USV) environment awareness. However, accurately perceived heading velocity and position of high speed USV in maritime scenario remains a challenge due to the limited availability of information and hardware cost. To address this issue, the newly released Orthogonal Time Frequency and Space (OTFS) modulation, which extracts Doppler shifts in the spatial domain and time delays, has been proposed to lift relative velocity and position accuracy. In this paper, we introduce a solution that leverages the OTFS waveform to continuously receive communication signals and identify delay-Doppler domain indices simultaneously. Specifically, we design a factor graph to realize belief propagation(BP), which has the potential to retrieve enough information to complete perception. Simulation results show that the proposed method yields significant improvements in velocity and position accuracy compared to the classic methods.