One of the key challenges in developing gel-based electronics is to achieve robust sensing performance, by overcoming the intrinsic weaknesses such as unwanted swelling induced deformation, signal distortion caused by dehydration, large hysteresis in sensing signal, etc. In this work, we proposed a structural gel composite (SGC) approach by encapsulating the conductive hydrogel/MXene with a lipid gel (Lipogel) layer through an in situ polymerization. The hydrophobic Lipogel coating fulfils the SGC with unique anti-swelling property at an aqueous environment and excellent dehydration feature at an open-air, thus leading to long-term ultra-stability (over 90 days) and durability (over 2000 testing cycles) for underwater mechanosensing applications. As a result, the SGC based mechanoreceptor demonstrates a high and stable sensitivity (GF of 14.5). Moreover, several SGC based conceptual sensors with high sensitivity are developed to unveil their profound potentials in underwater monitoring of human motions, waterproof anti-counterfeiting application, and tactile trajectory tracking.