In the late 18th century, rotting warships with their masts stripped away sat low in the River Thames, packed with hundreds of men. This episode traces how the prison hulk began as a stopgap. Britain had long shipped its convicts to the American colonies, and when the rebellion closed that route, courts kept handing down transportation sentences with nowhere to send anyone. In 1775 a private ship owner named Duncan Campbell offered the Home Office a vessel moored in the river, and by 1776 legislation had turned the holding pen into a sentence of hard labor lasting three to ten years.

The model spread quickly and at terrible cost. British prison ships in Wallabout Bay near New York, the HMS Jersey most infamous among them, killed 12,000 American prisoners during the Revolutionary War. On the Thames, a single typhus case forced the invention of quarantine and intake procedures. The episode follows the idea to Sydney Harbour’s school ships for wayward boys, to the Bay of Lubeck in May 1945, and into recent decades, where floating detention has served governments seeking distance from public view and from the law on land.

• One prisoner transferred from Maidstone Jail in October 1776 brought typhus aboard, and within seven months 28% of the prison ship population was dead.
• Reforms included washing and observing new arrivals for up to four days, two men to a bunk, and daily ox heads. Mortality fell from 18% in 1783 to 7% by 1786.
• French memoirs describing Napoleonic era hulks as extermination camps proved largely fictitious. Actual prisoner mortality ran between five and eight percent.
• On the Sobraon in Sydney, the commander aimed for a moral earthquake in every new boy, using marks and grades much like a token economy.
• New York’s Vernon C. Bain Correctional Center, opened in 1992, was a purpose built five story prison barge, and in 2009 the USNS Lewis and Clark held captured pirates.