As conductive hydrogels typically suffer from poor stability and swelling in water due to weak interfacial interactions, this study proposes a hybrid-crosslinking strategy to fabricate MXene/SA/PAM composite hydrogels. Specifically, a chemically cross-linked polyacrylamide network was formed via free radical polymerization, and sodium alginate was introduced to construct a semi-interpenetrating network serving as a flexible framework. The mechanical and electrical properties were further enhanced by incorporating MXene and Ca2+ coordination-based physical cross-linking. The surface functional groups (–OH/–O) of MXene improved the interfacial interaction with polymer chains, leading to increased mechanical strength. The resulting hydrogel exhibits outstanding mechanical properties (resilience: 99.5%). The incorporation of Ca2+,Cl?, and MXene established a dual ion–electron conductive pathway, endowing the hydrogel with high electrical conductivity (1.44 S m?1) and strain-responsive behavior. As a result, the hydrogel sensor can not only detect large-scale human motions such as joint bending but also accurately recognize written letters for smart touch-sensing applications. Moreover, the hydrogel demonstrates notable anti-swelling performance in various solvents, enabling applications in underwater information transmission (e.g., Morse code) and marine bio-monitoring. This work provides a promising approach for developing high-performance sensors suitable for motion sensing and underwater applications.