The prevention of biofouling attachment and growth on vessel hulls and other immersed surfaces has, and continues to be, primarily achieved through the use of antifouling paints, which continuously release one or more biocides through the paint surface. However, the environmental impact of antifouling biocides is of increasing concern and the search is ongoing for non-toxic methods 10 prevent biofouling. In addition to silicone fouling-release coatings and surface modification (considered elsewhere in this volume), fluorinated polymer coatings, smart polymers, hydrophilic surfaces, fibre coatings, scrubbable and inert coatings and non-leaching active coatings have all been investigated and considered as alternatives to biocidal antifouling paints. While most of these technologies do inhibit biofouling attachment and/or growth in various ways, none has yet provided a practical, widely applicable alternative for vessels. This is because either they have not been developed into a functional coating system or, if they have, they do not provide the long-term or broad spectrum efficacy needed to maintain the clean hull needed to optimise vessel performance and no translocation of harmful marine species.