A method of applying a protective coating to a surface under water which comprises forcing a protective coating composition through an applicator pad, for example using compreseed air, at a pressure at least equal to the ambient pressure of the water at the depth at which the coating is applied, and applying the coating composition to the surface by a smearing action of the pad. Apparatus for carrying out the method includes a porous applicator pad, a reservoir for a protective coating composition to be supplied to the applicator pad, a sensing device for sensing the ambient water pressure, and a control device operative to maintain the pressure at which the composition is supplied to the applicator pad at least equal to the sensed pressure. The applicator pad may be a layer of foamed plastics material having an open interconnected cellular structure.

A method and apparatus for removing marine fouling from underwater substrates such as ships' hulls (10). The method is characterized by the steps of first subjecting marine organisms such as barnacles to an electrical field of sufficent intensity to degrade the adhesive properties of the organisms to the substrate, and thereafter physically removing said organisms with the help of rotating brushes (16) or similar abrasive removal means. The apparatus is characterized in that it includes a remotely operated submarine (12) or other suitable transport means, such as a vehicle with a magnetized caterpillar track, having a forwardly mounted electrode (14) for imparting an electric field to the organisms together with abrasive removal means (16) mounted behind the electrode for removal of the organisms. A power source (18) is provided, having one pole (20) connected to substrate (10) and a second pole connected to electrode (14).