This paper investigates a novel locomotion mechanism that synergistically integrates tail-driven undulatory actuation with fin-induced frictional anisotropy to enhance propulsion efficiency and stability. A modular robot prototype was developed featuring a streamlined body, passive lateral fins, and active tail oscillation. The proposed control strategy generates continuous body waves via a feedforward sinusoidal scheme, while the inclined fins introduce directional-dependent frictional properties that modulate ground interaction.Experimental comparisons across three configurations—tail-only, fin-only, and combined tail-fins setups—demonstrate that the combined configuration achieves superior locomotion performance. These findings provide new insights into the design of amphibious robots capable of efficient and stable cross-medium movement by leveraging passive-active mechanical synergy rather than relying solely on morphological biomimicry.