Systems and processes for closing openings in marine vessel hulls are provided. The systems and processes facilitate repairs and maintenance of marine vessels by closing openings in the marine vessel hulls to permit dry access to compartments in communication with the openings. The processes and systems incorporate a cover constructed from a lightweight material such as fiberglass, a viscoelastic material such as polyethylene or polyurethane, and blends thereof. The cover is guided in place to effectuate closure of the opening by a track device that receives at least two of the peripheral edges of the cover and directs the cover to the proper position to close the hull opening. The cover may be lowered into place by use of a hoisting device such as a davit.