Synergistic Hydrophobic and Hofmeister Effects Drive Recyclable, Tough, and Antiswelling Hydrogels for Underwater Communication

). The dynamic physical cross-links enable full recyclability, with the material retaining over 80% of its mechanical strength after three reprocessing cycles. When applied as an underwater strain sensor, RTASH exhibits high sensitivity (GF = 0.6), fast response (0.3 s), and long-term stability over 60 days of continuous operation. Leveraging its tunable electromechanical properties, we demonstrate real-time Morse code communication underwater including the reliable transmission of SOS distress signals. This work presents a straightforward and sustainable material fabrication strategy to advance the development of environmentally adaptive underwater communication systems.