Tress of the Emerald Sea reveals the impact of one’s surroundings and experiences on identity; identity is fluid, changing as one’s life changes. Both Tress and Charlie become different people through their journeys. Their fundamental values remain, but broader experiences allow them to learn about themselves and others more deeply, altering their paths. When Hoid introduces Tress and Charlie to the reader, they are both unassuming people. Tress washes windows, cares for her family, and collects cups from sailors passing through the Rock. Even her parents note that she never asks for anything—she never wants to impose, and she is content with her life on the Rock. Charlie, despite being the son of a cruel duke, is kind and loves telling stories. Neither of them wishes to be a hero.

The duke’s actions, however, change their situation. As Hoid (as narrator) explains, “Truth is, people are as fluid as time is. We adapt to our situation like water in a strangely shaped jug, though it might take us a little while to ooze into all the little nooks” (388). By sending Charlie to the Sorceress, the duke forces Charlie into a cursed life. Tress at first believes she is helpless in the situation, hopeless and continuing her life on the Rock.