The marine coating in the tidal zone is crucial to restoring its protective function in the case of coating defects, mainly due to the structural damage of the coating by the alternation of wet and dry in the tidal zone and the surface damage of the coating by the impact of sand and gravel. Hydrophilic materials such as hydrogel transformed the tidal zone into an entire immersion zone. Due to the complexation of copper, the fouling problem can be effectively reduced. The coating (AAm/Alginate‐Ca/Cu‐BTA) has excellent mechanical properties (modulus: 200 kPa, toughness 128 J m−2) and significant adhesion (138 J m−2). Otherwise, herein, simultaneously mechanical tests of hydrogels at different temperatures and excellent mechanical properties (modulus: 160 kPa, toughness 100 J m−2) after 7 days of use in alternating dry and wet environments every 6 h are shown. It's proved that the coating has an excellent antifouling and anticorrosion effect. Meanwhile, theoretical study reveals the nature of the weak mechanical properties of hydrogel materials at low temperatures. This work provides an effective strategy for preparing hydrogel coatings with excellent mechanical properties and marine anticorrosion and antifouling. It also proves that hydrogels have broad application prospects in marine tidal zone by excellent water retention performance.