Etymologically, island means ‘watery land’ (Beer 1990, 271). Article 121 of the United Nations Convention on the Law of the Sea (1982, 66) defines an island as ‘a naturally formed area of land, surrounded by water, which is above water at high tide’, adding that ‘the territorial sea, the contiguous zone, the exclusive economic zone and the continental shelf of an island are determined in accordance with the provisions of this Convention applicable to other land territory’. The article was hotly debated from 1972 to 1982, and points to the political and economic implications of what is included and excluded in the definition of an island in a period when many islands were in the process of decolonization. The decolonization of Caribbean and Pacific islands refers us back to early modernity, when Europeans began to ‘see islands everywhere’ and ‘think with islands’ (Gillis 2004, 1–4), and any history of travel writing should consider the central role occupied by islands in the Western imagination.

The relationship between water and land is central to a discussion of islands. In antiquity, Iamboulos's utopian Island of the Sun is reached after the travellers have lost their way at sea in a storm, and Odysseus is blown from island to island; water is here a dangerous element that needs to be crossed. As John R. Gillis (2004, 9–21) argues, Western civilization was long uncomfortable with the sea despite ‘mental voyages into the unknown’. In medieval times, Marco Polo and John Mandeville offered fantastic accounts of islands populated by monsters and magicians, yet the island setting was often a mere backdrop to the narrative (Van Duzer 2006, 148–49). Islands were also important in the immrama, tales of sea voyages by Irish Saints, notably the Voyage of Saint Brendan, which recounts the search for a paradisal island in the West, combining a scriptural spatiotemporality and a carefully hedged secular fascination with the tumultuous interplay of land and water. Columbus's mental geography and his accounts were shaped by the archipelagos of Marco Polo, Saint Brendan and others; these islands also found their way into the isolario, a genre that appeared in the fifteenth century and contained maps as well as descriptions of real and legendary islands.