Abstract: A process for extending the life of an antifouling paint film which comprises applying onto an antifouling paint film a coating of a water-permeable graft polymer prepared by polymerizing one or more vinyl monomers in the presence of a hydrophilic polymer. The coating of the water-permeable graft polymer has an excellent water-resistance and a proper water-permeability by which an antifouling agent contained in the antifouling paint film can be leached into sea water and moreover the leaching rate can be controlled. As a result, the antifouling property of the paint film is exhibited for a long period of time.