Maritime history is difficult to locate with any spatial precision. Where in the watery expanses of the Atlantic did Columbus’s crews threatened to mutiny? Where off the Azores in 1592 did an English naval squadron seize the fabulously rich Portuguese carrack, Madre de Deus, with its astounding cargo of spices and jewels from the East? Where in the middle passage from Africa to Jamaica did the crew of the Zong send 133 enslaved Africans to their deaths in 1781? Where are the burial sites of the millions of immigrants who died at sea? With oceanic space, there is no way to mark a grave, erect a plinth, investigate the scene of the crime, run a boundary, or post a commemorative plaque.