<p>Accumulation of aquatic organisms on submerged sea vessel surfaces increases drag, resulting in higher fuel consumption and more greenhouse gas emissions. Polymer coatings hold promise to combat marine biofouling as more environmentally friendly alternatives to metal-based paints. While hydrophilic coatings are known to lose antifouling efficacy upon sediment adsorption, how to arrange hydrophobic segments and develop a sufficiently thick coating layer to suppress diatom deposition in the presence of silt and maximize the antifouling performance has been unknown. Here, we developed an effective and scalable antifouling coating by combining the polydopamine precoating method with well-defined amphiphilic copolymers synthesized using a controlled polymerization technique. Reversible addition-fragmentation chain transfer copolymerization of zwitterion-containing hydrophilic sulfobetaine methacrylate and hydrophobic trifluoroethyl methacrylate produced the target copolymers with control of composition, molecular weight, and sequence. Zr(IV)-mediated coordination bonds between polydopamine and sulfobetaine groups yielded &gt;20 nm thick films stable for a month in seawater. The random copolymer sequence exposed both hydrophilic and hydrophobic groups on the outermost coating surface. Synergistic repelling diatom and silt led to the best antifouling performance at the optimal hydrophilic-hydrophobic balance. Superior antifouling efficacy was retained for a month and was also effective on stainless steel, suggesting the potential for practical application.</p>