All surfaces immersed into oceanic or fresh water environments are subjected to the attachment and accumulation of aquatic organisms, a phenomenon known as biofouling. The adhesion of micro- and macro-organisms has disadvantageous effects for numerous technical applications, from shipping to power plant cooling systems to food processing industries. The negative impact of biofouling on ships includes higher fuel consumption caused by the increase of drag resistance and total weight gain, as well as material damage due to of biocorrosion. The attachment of organisms can be reduced by a variety of strategies, for example self-polishing surfaces, leaching toxins or repulsive substances for microorganisms, or specific physico-chemical surface properties in general. The development of environmentally friendly antifouling paints is crucial from an ecological point of view. One approach to tackle biofouling is the usage of fouling-release coatings, which are non-toxic and prevent permanent attachment of marine organisms to the surface by their low surface energy. We present a composite material which overcomes one of the most prominent disadvantages of existing fouling-release coatings: their low mechanical stability. This is achieved by taking advantage of phase separation between hydrophobic polydimethylsiloxane (PDMS) and hydrophilic polythiourethane (PTU). The rubber-like silicone (PDMS) forms isolated hydrophobic domains on the composite’s surface while PTU constitutes a mechanically stable polymer matrix. By adding tetrapodal ZnO particles (t-ZnO), the distribution of the hydrophobic domains on the surface of the composite can be modified. After investigating mechanical performance, adhesion, surface and biofouling properties of the composite, we can state that we were able to produce mechanically stable and strongly hydrophobic polymer composites with enormous potential in maritime applications.