L'Engle draws from a number of literary genres and conventions in Dragons in the Waters. It is a quest story, a Gothic mystery, and a detective story, all wrapped up in one. As the voyage to Venezuela progresses, it becomes clear that Simon is searching for his family heritage as symbolized by the true story of Quentin Phair. This quest leads him to discover unsettling truths about Quentin, such as his betrayal of those who most trusted and cared for him.

When Simon finds himself running from danger and betraying his own friend, Canon Tallis, he must confront his own, as well as his ancestor's, weaknesses.

The story-within-a-story about Quentin Phair comprises one half of the mystery plot; the other half concerns the shipboard murder and the portrait of Bolivar. This second half of the plot more closely resembles a conventional detective story, except that there...