Superoleophobicity under seawater: An ion-induced low-oil-adhesion film with underwater superoleophobicity is prepared by a typical layer-by-layer (LBL) method. Under an artificial marine environment with high ion-strength, the prepared polyelectrolytes/AuNPs hybrid film becomes rougher and possesses a higher water ratio, which in turn endows the film with superoleophobicity and low underwater oil adhesion. The as-prepared film shows excellent environmental stability in artificial seawater. This study provides a new strategy for controlling the self-cleaning property and accelerating the development of stable underwater superoleophobic films.