Aboard the Anne in La Rochelle harbor, Marguerite settles a trembling, terrified Damienne in the forecastle, then is led by Roberval to their cramped quarters below: a small dining cabin with bunks for the navigator and secretary, and a tiny adjoining chamber for Marguerite and Damienne. Damienne, dreading the sea, likens the room to a coffin and grows increasingly disoriented as days pass waiting for wind, confusing day and night and wishing for death. Marguerite tries to keep her nurse eating, breathing fresh air, and oriented in time.

While Damienne fades, Roberval flourishes, ruling his fleet of three ships with jovial authority. He instructs Marguerite in the workings of the vessel—the whipstaff, hourglass, and astrolabe—displaying his power even through his apparent kindness. Marguerite has come to fear his approval as much as his anger.

On the fifth morning, the anchor is raised and the fleet sails from La Rochelle to trumpets and cheers. Watching her homeland recede, Marguerite reflects that, having funded the voyage with her inheritance, she is the instrument of her own exile. The secretary joins her at the rail, and in a coded exchange Marguerite admits she fears drowning and Roberval. The secretary tells her Roberval wants greatness and demands obedience in heart and mind—but quietly admits he himself does not give it, allying himself with Marguerite.

That night Damienne suffers vertigo and nausea, and Roberval, disgusted, initially bars her from the table. Marguerite pleads successfully for her inclusion. After dinner, the navigator and secretary play chess; Marguerite watches curiously, asking about the castle piece. The secretary then plays a graceful galliard on his cittern, charming everyone—including Damienne—until Roberval, displeased by the praise, seizes his own cittern and overpowers his servant's playing with brilliant, forceful technique, reasserting his dominance.