Prison Ships
During the time that Great Expectations was written, Australia was a colony of England. For convicts held in prison in England, they knew that they had a high probability of ending up in Australia. Prisoners were sent to Australia to farm and work on the land with the residents of the land as indentured servants. Therefore, they would get money. It wasn't a bad deal. After their amount of work was up, most of the convicts decided to work alongside their master before and they would run their business together. The ships were made as residencies for the prisoners while they were still in England. They would have their cells on board and they would stay on the ship until the ship was allowed to depart for Australia. But once they went to Australia, the convicts were often banned from ever returning to England. And if they did return and if they were caught, they would be sentenced to death.