This article focuses on the consolidation of naval hygiene practices during the Victorian era, a period of profound medical change that coincided with the fleet’s transition from sail to steam. The ironclads of the mid- to late- nineteenth century offered ample opportunities to improve preventive medicine at sea, and surgeons capitalised on new steam technologies to provide cleaner, dryer, and airier surroundings below decks. Such efforts reflected the sanitarian idealism of naval medicine in this period, inherited from the eighteenth-century pioneers of the discipline. Yet, despite the scientific thrust of Victorian naval medicine, with its emphasis on collecting measurements and collating statistics, consensus about the causes of disease eluded practitioners. It proved almost impossible to eradicate sickness at sea, and the enclosed nature of naval vessels showed the limitations – rather than the promise – of attempting to enforce absolute environmental controls. Nonetheless, sanitarian ideology prevailed throughout the steam age, and the hygienic reforms enacted throughout the fleet showed some of the same successes that attended the public health movement on land. It was thus despite shifting ideas about disease and new methods of investigation that naval medicine remained wedded to its sanitarian roots until the close of the nineteenth century.