Prison hulks were ships used to accommodate British convicts. The ships were anchored on the Thames River and in the naval harbors of southern England. This system was adopted in 1776, after American opposition forced the British government to stop the transportation of convicts to the American Colonies. Convicts on the hulks labored during the day on public works projects, such as dredging sand and silt. By the standards of that time, the system worked fairly well. The conditions on the hulks seemed better than those in ordinary prisons of the time. But there were periodic outbreaks of disease on the hulks. Prison reformers also opposed the hulks because the crowded conditions lowered morale among prisoners.