It's clear to see that Antoinette and Rochester's marriage is a failure. It came crashing down in flames (literally?). In the end Antoinette's insanity is responsible for their total separation. But one could argue that their relationship was doomed from the start.
Throughout the whole novel there are themes of being displaced. The first part of the book, narrated by Antoinette, shows how much Antoinette feels like a stranger in her own home. The black Jamaicans hate her family because they are ex-slave-owners. The white people hate her family because they are left extremely poor after Antoinette's father dies. Her childhood is tormented with rumors of her mothers madness and names like "white cockroach". Antoinette is left an extremely lonely character.
The second part is mostly narrated by Rochester, Antoinette's new husband. We learn that Rochester lives in the shadow of his older brother and by the English laws of primogeniture is left without a share of his father's fortune. He resents his brother as well as his father for picking favorites. He has come to Jamaica to attain a rich wife so he can not only sustain himself but prove to his family that he is worth something.
Antoinette and Rochester's marriage stands on the extremely rocky foundation of two people that are uncomfortable with their situation. This is where the title of the book comes in. The Sargasso Sea lies in the Atlantic Ocean between the West Indies and Europe. It is known for its tumultuous waters. This represents the attempt at a connection between Antoinette and Rochester. Rhys suggests that the Sea is too wide for their relationship to work. Their backgrounds are just too different. Antoinette has money but is respected by no one. She needs an actual friend. Rochester comes from a respected family but has no money on which to stake his claim. He finds Antoinette and uses her to fill in the holes that will allow him to maintain his position in society. The only thing they have in common is that they each have a troubled past. And that is nothing to stand on.
