In Herman Melville's "Moby Dick," the quote reflects on the duality of human nature, suggesting that even those who appear virtuous may harbor darker instincts. The mention of a "shark" symbolizes the primal, aggressive aspects of one's character, while the "angel" represents restraint and morality. The quote encourages introspection, prompting readers to consider their inner conflicts between instincts and ideals.

By comparing the two, Melville conveys that true virtue may involve mastering these inner "sharks" rather than eliminating them. The struggle between these opposing forces defines human experience, emphasizing that moderation and self-control are crucial in achieving a balanced existence.