The prohibition of highly efficient tributyltin-based antifouling coatings in 2008, as well as the upcoming EU regulation which contains the approval of any antifouling substance, leads to the necessity of new solutions. In the present work, a solvent free two-component polythiourethane (PTU) was combined with tetrapodal-shaped ZnO (t-ZnO) microparticles in order to fabricate a mechanically durable and environmentally compatible coating which can be realized on a large scale. Different PTU/t-ZnO composites were therefore fabricated and characterized with respect to mechanical and chemical features. Preliminary experiments were carried out in seawater tanks where strongly reduced growth was shown for composites with high t-ZnO content . Advanced immersion experiments were carried out in the Baltic Sea (Laboe harbor, Germany) in order to evaluate the growth behavior on the different PTU/t-ZnO composites under natural conditions. After one year of immersion, all samples were homogeneously fouled by hard and soft elements (algae, barnacles, mussels) indicating the ability of organism to stick to the developed surfaces. However, subsequent cleaning experiments with a high pressure water jet device caused perfectly rinsed surfaces with no signs of biocorrosion for the PTU/t-ZnO composites. Remarkably, all immersed references (PVC, steel) were highly degraded by residual barnacle cement.