Coffin ships refers to the concept of ships that were no longer sea worthy, but had been brought and repainted and even renamed to appear as new. With the law on the side of the ship owners sailors had no way of evading going upon these ships and dying. To refuse to sail upon a ship once you had signed you agreement would result in prison, and destitution for the sailors family. Many sailors – when given a choice between been handsomely paid and risking their lives, or destitution and the ruination of their family – would take the risk of these coffin ships. Many would die and would cause Samuel Plimsoll to have his outburst.
Read more: http://www.telegraph.co.uk/culture/books/3653529/Saving-lives-at-sea.html