The ship resistance penalties of slime, shell and weed are discussed in turn. Methods to measure the hard paint roughness of antifouling coatings are recapitulated. The determination of a satisfactory roughness parameter from correlations with measured roughness functions is described. This in turn, allows a relationship between ship added friction and roughness height to be found. This recapitulation allows consideration of using the same route for a surface with filamentous fouling. Consideration is given to low surface energy coatings and their roughness idiosyncrasies. The determination of economic penalties is discussed, both for a particular ship and globally.