Inspection and/or maintenance method and associated apparatus

An isolation method for isolating and temporarily sealing closed an opening of a marine vessel to prevent ingress of fluid into or through the opening, sealing an internal side of the opening from an external side of the opening, the isolation method comprising sealing the opening with a sealing apparatus, wherein the method comprises:

• connecting the sealing apparatus to at least one connection point associated with the opening of the marine vessel, the connection point being used to connect a positioning line relative to the opening;
• providing the positioning line between the connection point and the sealing apparatus;
• tensioning the positioning line such that the sealing apparatus is pulled towards the connection point to maneuver the sealing apparatus into a desired position relative to the opening;
• and
• sealing closed the opening with the sealing apparatus;
• wherein the method is performed entirely diverlessly, with no personnel required in or under the water at any stage of the method, including connecting the positioning line relative to the connection point and pulling the sealing apparatus onto and/or into the opening.