This study decodes the BDS-3 PPP-B2b binary data broadcast by BDS satellites using a self-developed software decoder, RT-B2b (Real-Time PPP-B2b). The orbit, clock corrections, and differential code biases (DCB)—collectively referred to as State Space Representation (SSR) corrections—are extracted from the decoded messages. Subsequently, precise satellite orbits and clock offsets are recovered in real time by integrating the SSR corrections with the broadcast ephemeris. The characteristics and accuracy of the SSR corrections are first evaluated. The performance of real-time PPP is then assessed through both static and kinematic experimental schemes, with particular emphasis on the kinematic positioning of a marine buoy. The results demonstrate that the developed software decoder can reliably decode the PPP-B2b SSR corrections and derive accurate orbit and clock products. In terms of positioning performance, real-time PPP achieves centimeter-level accuracy of 4–5 cm in static terrestrial scenarios and decimeter-level accuracy of 1–2 dm in the kinematic marine buoy scenario. This study validates the reliability of the PPP-B2b real-time service in marine environments, thereby providing a valuable reference for marine precise positioning and the practical application of high-accuracy positioning information.