A method and apparatus for the cleaning of an underwater surface, such as a hull. The method and apparatus enables cleaning to be conducted while mitigating the release of removed material into surrounding waters. The integrated apparatus includes a cleaning deck for removing fouling from the underwater hull surface, and a pre-processing deck with integrated components for the processing of cleaning effluents. According to the method and apparatus, materials removed by the shroud are sucked into the pre-processing deck, crushed, and separated into a separator effluent that may be recycled to the shroud, and a concentrate, which is discharged to a land treatment unit for further processing.