Versatile electrocatalysis at higher current densities for natural seawater splitting to produce hydrogen demands active and robust catalysts to overcome the severe chloride corrosion, competing chlorine evolution, and catalyst poisoning. Hereto, the core‐shell‐structured heterostructures composed of amorphous NiFe hydroxide layer capped Ni3S2 nanopyramids which are directly grown on nickel foam skeleton (NiS@LDH/NF) are rationally prepared to regulate cooperatively electronic structure and mass transport for boosting oxygen evolution reaction (OER) performance at larger current densities. The prepared NiS@LDH/NF delivers the anodic current density of 1000 mA cm−2 at the overpotential of 341 mV in 1.0 m KOH seawater. The feasible surface reconstruction of Ni3S2‐FeNi LDH interfaces improves the chemical stability and corrosion resistance, ensuring the robust electrocatalytic activity in seawater electrolytes for continuous and stable oxygen evolution without any hypochlorite production. Meanwhile, the designed Ni3S2 nanopyramids coated with FeNi2P layer (NiS@FeNiP/NF) still exhibit the improved hydrogen evolution reaction (HER) activity in 1.0 m KOH seawater. Furthermore, the NiS@FeNiP/NF||NiS@LDH/NF pair requires cell voltage of 1.636 V to attain 100 mA cm−2 with a 100% Faradaic efficiency, exhibiting tremendous potential for hydrogen production from seawater. Herein, core‐shell structured Ni3S2‐FeNi layer double hydroxides (LDH) heterointerfaces are rationally prepared. Abundant hydroxide/sulfide interfaces boost alkaline water oxidation. Impressively, electrochemical results indicate that the in situ formed sulfate layer in LDH shell largely enhances the corrosion resistance of the catalysts in the alkaline salty‐water electrolytes.