Integrating a self-healing function into soft nanorobots composed of polymers can extend their lifespan, particularly in harsh marine environments. While existing strategies have explored dynamic interactions to enable underwater healing of polymer materials, significant challenges remain, owing to compromised mechanical integrity and inefficient healing in water. Herein, we report underwater self-healing polymer materials via a seawater-adaptive network reconstruction. Controlling the catechol-functionalized polymers and their microphase nanostructures could enhance mechanical strength in an aqueous environment. Upon damage, the surrounding water induced plasticization and promoted the hydrogen-bonding network reorganization of the polymer. Simultaneously, catechol groups sequestered Ca2+/Mg2+ ions from seawater, enabling a cross-linking reaction at fractured interfaces autonomously. After self-healing in artificial seawater, the soft polymer nanomaterial achieved an excellent tensile strength of 23.7 MPa. Furthermore, the strong intrinsic self-healing polymers maintained their high tensile strength in an aqueous environment. These polymers are intrinsically homogeneous, providing consistent mechanical properties and an efficient self-healing capability in aqueous environments. Hence, integrating these polymers into marine soft nanorobotics could address the challenges in the harsh conditions of the deep sea.
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