After retiring as the University of Florida president emeritus in 1984, Marston returned to the Virginia Military Institute as a distinguished scholar, and later served on VMI's governing Board of Visitors during the controversy over the court-ordered admission of women. In 1985, he went back to the University of Florida faculty and conducted research and presented papers for the university's Department of Fisheries and Aquatic Sciences and its College of Medicine, co-edited "The Medical Implications of Nuclear War" on behalf of the National Academy of Sciences, and served as the chairman of the Safety Advisory Committee for the Clean-Up of Three Mile Island. He also accepted the chairmanship of the Florida Marine Fishery Commission, tasked with the governance of the state's saltwater fishing industry and guardianship of its resources.