While liquid-like surfaces show promise for protecting underwater optical systems against biofouling and mechanical degradation, creating transparent, fluorine-free omniphobic coatings that combine mechanical robustness with flexibility and long-term durability remains a critical unmet challenge. Here, an innovative dual-curing hybrid approach is reported that synergistically incorporates multi-functional polymers within an epoxy matrix to form a densely cross-linked yet flexible network. This unique architecture achieves an unprecedented balance of high hardness (7–9H) and extreme flexibility (10 000 bending cycles, bending radius = 1 mm). The interpenetration of organosilicons confers exceptional omniphobicity and anti-adhesion characteristics, enabling low-surface-tension liquids to slide off readily (sliding angle < 4.1°). Fabricated through an environmentally benign, one-step, solvent-free process, the optimized coating demonstrates remarkable substrate adhesion (5B) and exceptional wear resistance, ensuring reliable operation in demanding underwater environments. The highly cross-linked network maintains exceptional stability in aggressive liquid media without compromising optical transparency (> 99.1%). This work not only overcomes the fundamental trade-off between mechanical robustness and flexibility but also establishes a generalizable platform for designing high-performance protective coatings for marine optical applications.