Marine fouling is attaching organisms to objects floating or submerged in seashores, such as ships, docks, and offshore structures. The impact caused is the reduced lifespan of the thing attached to the biofouling. In addition, there was a spread of invasive species. The government and industries in the United States spend over 6.5 million dollars annually on their budget to overcome this problem. So far, the prevention of marine biofouling is using antifouling paint on ships and submerged structures. One of them is organotin tributyltin (TBT) proven effective for preventing fouling; however, it is not environmentally friendly. Sponge Siphonodictyon coralliphagum growing in Salibabu Island waters, Talaud Islands, with previously shown activities against prokaryotes, was collected and extracted by maceration using ethanol as a solvent. The extract was then added to the base paint with several compositions of 5%, 10%, and 25% applied to the paving block surface. Positive control uses paint with copper additives. The objects are then immersed in the seashore below subtidal depths. The observation was carried out every seven days until day 28. The paving block was observed on day 90 after immersion. Significant results were obtained where macrofouling was only able to grow in negative control and positive control. The extract sponge S. coralliphagum has vigorous antifouling activity against marine biofouling. Furthermore, the extract was fractionated using liquid chromatography and continued by testing their activity against Gram-positive and negative bacteria. Further investigation of NMR spectra from the active fraction to prokaryotic cells shows a cyclic aliphatic compound with several keto-enol functional and methyl aliphatic groups on their chain.