Abstract: To address the payload constraints of underwater vehicles and the scarcity of underwater spectral resources, a tri-path channel comprising direct, surface-reflected, and bottom-reflected acoustic paths is proposed. Based on this model, a frame structure integrating communication and speed sensing is developed using a preamble function multiplexing scheme. Joint estimation of Doppler shift factors and signal arrival times are accomplished under different acoustic path combinations. This approach fulfills the dual functions of speed sensing and signal synchronization. Experimental results demonstrate that, with a high-frequency preamble designed for a 4 kHz bandwidth, a communication rate of 1.4 kbit/s and a bit error ratio of 0.19% are simultaneously achieved by the integrated signal, enabling reliable information transmission. In terms of velocity sensing, the target motion velocity is set at 0.1 m/s. Compared to the baseline model considering only the direct path, the velocity measurement performance is improved by 27.68% when the surface reflection path is incorporated. When the bottom reflection path is further included to form a tri-path model, the velocity measurement performance is improved by 71.39%.