When the husband describes the passionate aspects of their relationship, he uses death as a metaphor for orgasm. This corresponds with a French idiom from the 17th century, la petite mort. In this section, Rhys also makes an allusion to Shakespeare, as Antoinette articulates herself in a way that is reminiscent of a line spoken by the titular character of Othello.
In the early part of the honeymoon, before Daniel's letters have damaged the husband's view of Antoinette, they spend their evenings in intimacy. The husband recalls a night when Antoinette asks whether he would take her life, now when she feels complete bliss.
"If I could die. Now, when I am happy. Would you do that? You wouldn't have to kill me. Say die and I will die. You don't believe me? Then try, try, say die and watch me die."
"Die then! Die!" I watched her die many times. In my way, not hers.
The first two sentences in Antoinette's portion of dialogue are reminiscent of a pair of Othello's lines from the second act of Othello: "If it were now to die / 'Twere now to be most happy." When he speaks these lines, Othello has just been reunited with his wife Desdemona. Overjoyed to see her again, he claims that he would be fine with dying in this moment. Similarly, Antoinette feels so happy and safe in her marriage that she claims this would be a good time to die. This sheds light on her fragile emotional state. Accustomed to feeling vulnerable, she responds to contentment with a suicidal urge.
Naturally, the husband does not agree to take Antoinette's life, but he does agree to make her die in a metaphorical sense. Death is a common euphemism for orgasm. Through his idiomatic language, he conveys that they have a lot of sex during this period. They make each other "die" "in sunlight, in shadow, by moonlight, by candlelight."