A physician and naturalist joining the British Navy as the ship's surgeon, offering insight into both human and animal behavior. Of Irish Catalan descent, he is characterized by his small stature, pale complexion, and intellectual pursuits.

The Irish Catholic lieutenant on the ship, serving as a stern and honorable presence with a conflicted sense of loyalty. Known for his dark-red hair and green eyes, he presents a foil to Aubrey with shared bravery but differing backgrounds.

The wife of a captain with whom Aubrey is romantically involved, known for her commanding presence and beauty. She is musically inclined, often drawing attention at social gatherings.