Surfaces submerged in the marine environment are often fouled by bacteria, algae, or macro-organisms. It is well established today that fouling on ships increases the hull roughness, causing increased frictional resistance and fuel consumption, as well as decreased top speed and range1. It has been estimated that the US alone spends more than $5B annually to prevent and control marine biofouling. Antifouling (AF) coatings have been widely used to control the problem, but they contain biocides which are toxic to marine organisms, resulting in a worldwide ban. As research on non-toxic alternatives is ongoing there is a pressing need to assess the impact of various types of fouling and coverage level on the frictional resistance of naval vessels to make cost/efficient hull cleaning decisions. In turbulent boundary layers over rough surfaces the equivalent sandgrain roughness, ks, is used as a common currency to estimate hydrodynamic resistance2. For biofouled surfaces, however, estimating ks, via correlations based on datasets from generic rough surfaces leads to significant errors because biofouling has unique surface properties (i.e. high skewness, low effective slope, ES < 0.16 etc). The objective of this session is to bring together experts with diverse backgrounds, including biology, material science, experimental and computational fluid dynamics to provide a snapshot of the state-of-the-art, and identify future needs and research directions in the field.