Abstract: With the continuous enhancement of refinement for marine engineering projects in China, higher requirements have been imposed on the stability and autonomous controllability of high-precision marine positioning. Therefore, it is imperative to analyze the high-precision positioning performance of the BeiDou Navigation Satellite System (BDS) in marine environments. This paper employs measured Global Navigation Satellite System (GNSS) data from the northern part of the South China Sea and utilizes the Precise Point Positioning with Ambiguity Resolution (PRIDE PPP-AR) software developed by Wuhan University to conduct Precise Point Positioning (PPP) experiments using single BDS, single Global Positioning System (GPS), and full GNSS constellation. A comparative analysis of the positioning results is then carried out. The results indicate that, in Haikou, Hainan, the accuracy of static simulated kinematic PPP results is comparable across the three modes of single BDS, single GPS, and full GNSS constellation, with the full GNSS constellation achieving the highest accuracy, surpassing 0.05 m in all three directions. In the northern South China Sea, the geometric configuration of single BDS observations is superior to that of single GPS. When referenced against PPP results from the full GNSS constellation, the PPP results from single BDS exhibit a high degree of agreement, with Root Mean Square Errors (RMSEs) in the horizontal and vertical directions being better than 0.01 m and 0.02 m, respectively, significantly outperforming the single GPS PPP results. When referenced against relative positioning results, the accuracy of single BDS PPP is consistent with that of the full GNSS constellation PPP and is approximately 0.05 m higher than that of single GPS PPP. Furthermore, Moreover, the dynamic PPP positioning results derived from single BDS data sampled at 10 Hz or higher contain centimeter-level dynamic positional signals that are not present in the results from 1 Hz sampled data, positioning results derived from single BDS data with a sampling rate of 10 Hz or higher contain centimeter-level dynamic positional information that is not captured by data sampled at 1 Hz, indicating that high-sampling-rate BDS data can effectively support deformation monitoring requirements in dynamic marine environments.