Luxury waterproof necklaces typically use materials such as stainless steel or solid gold—not only for their aesthetics but for their inherent resistance to tarnish and corrosion. Many are enhanced with PVD (Physical Vapor Deposition) plating, providing superior protection against water, sweat, lotions, and perfumes, while retaining their original luster. Hey Harper’s waterproof necklace collection, for example, features PVD-coated chains backed by lifetime color warranties