The title of the novel refers to the Sargasso Sea, a vast area of the northern Atlantic Ocean which is home to sargassum, a kind of seaweed. The Sargasso Sea is legendary for being an oceanic black hole, where ships get ensnared by huge forests of floating seaweed, or drift helplessly when the wind ceases to blow.
The title invites the reader to consider how the characters can be thought of as trapped in their own Sargasso Seas. They may be suspended in the murky passage between two worlds, between England and Jamaica, for example, or between racial identities, as Antoinette struggles with her white Creole heritage. But the terrors of the Sargasso Sea are also largely mythical, the product of sailor lore rather than historical or scientific fact. By linking itself to this mythical tradition, the novel asks the reader to consider the role of stories and fictions in the characters' lives, particularly when it comes to encountering experiences that are foreign, alien, and strange.