While boys had a long history of serving with the Royal Navy and Merchant Marine, greater attention began to be paid to their recruitment following a manpower shortage in the mid-nineteenth century. Traditional naval training venues, such as the Greenwich Hospital School, steadily improved their standards of admission, while charities established ‘training ships’ to prepare boys for a life at sea. Although intended to recruit boys from disadvantaged backgrounds, these schemes were highly selective: only ‘healthy, respectable boys’ were desired for the sea services. For those who met the rigorous fitness standards, the naval schools offered almost unparalleled attention to the factors affecting healthy physical development—careful attention was paid to the boys’ diet and exercise regimes, and constant adjustments were made to their schedules and provisions to ensure that they would grow into robust seamen by the time they graduated. While these initiatives were often short-lived (waxing and waning with manpower needs), they showed an increasing prioritisation of the health and welfare of adolescents who were expected to maintain Britain’s supremacy of the seas.