This purely expository chapter clearly foreshadows Edna's death and establishes its cause as the process of self-discovery which she has just begun, a process facilitated by her contact with the warm Gulf waters. She is starting to understand the limitations of and feel constrained by the expectations of her culture.
This chapter establishes Edna's relationship to the sea and its role as a catalyst in her awakening to herself, her needs, and her desires. Edna is beginning to see a "certain light . . . the light which, showing the way, forbids it." While in the previous chapter she resented Robert's head on her arm, the resentment may have sprung from the recognition that she could not respond in kind, not free to explore the parameters of passion that Robert affects — passion that her husband doesn't pretend to possess. The sea, where she swims with Robert, appeals to and awakens her innate sensuality. The warm waters of the Gulf of Mexico are "sensuous, enfolding the body in its soft, close embrace" much as a lover would, but also as the muffling touch of death. The water's seductive voice compels Edna's soul to "lose itself in mazes of inward contemplation," a symbol of how her burgeoning interest in realizing her own desires and needs overcomes the maintenance of her life as she knew it, ultimately taking her very life itself.
Note that Chopin repeats sentences from the final two paragraphs of this chapter in the novel's final chapter, when she describes Edna's fatal swim.
vouchsafe to be gracious enough or condescend to give or grant.