Marine paint mixed with 2-methoxy-2',4'-dichloro chalcone is able to considerably reduce the formation of biofilm by Vibrio natriegens, a marine bacterium, on polycarbonate (PC), polymethylmethacrylate (PMMA) and glass fiber reinforced plastic (GFRP). These polymers have been selected for the study, since they have wide marine applications. Surfaces coated with dichloro chalcone containing marine paint had the lowest number of colony forming units (CFU) (1-5×106), proteins (20-30μg/cm2) and carbohydrates (5-10μg/cm2) attached to them after 28 days of exposure to the organism when compared to surfaces coated with CuSO4 mixed paint (20-40×106CFU/ml, proteins of 50-60μg/cm2 and carbohydrates of 40-50μg/cm2) or plain marine paint (30-40×106CFU/ml, proteins of 120-150μg/cm2 and carbohydrates of 40-60μg/cm2). At the end of the study period, the biofilm on PMMA was 7, 10 and 12μm thick on chalcone, copper and plain paint coated surfaces, respectively. The first two paints increased the surface roughness but decreased the surface hydrophobicity when compared to the plain paint. Large number of dead cells was found on the chalcone mixed and predominantly live cells were found on plain paint coated surfaces. 15% of dichloro chalcone had leached out of PMMA surface after 28 days. The low amount of biofilm formed in the presence of dichlorochalcone can be associated to its antibacterial and slimicidal activity and also its ability to reduce the hydrophobicity of the surface. This dichlorochalcone appears to be a novel agent for decreasing the formation of marine biofilm. © 2010 Elsevier B.V.