Abstract: Traditional motor-driven solutions face challenges in meeting the requirements of legged robots for underwater engineering operations, including complex waterproof sealing design and high manufacturing costs. To meet the current requirements for underwater engineering operations, in this study, a single leg model was proposed, which driven by water hydraulic artificial muscles using water as the driving medium, fundamentally avoiding these issues. Firstly, a joint module was designed based on the antagonistic action of two water hydraulic artificial muscles. On this basis, joint modules were connected in series to form a single leg prototype, and a test platform was established. Leg joint motion experiments were then conducted based on kinematic analysis. The experimental results showed that the single leg driven by water hydraulic artificial muscles can satisfy motion control requirements, laying a foundation for subsequent research on water hydraulic multi-legged robots.