At the start of The Sweetness of Water, Isabelle comes across as a rather reclusive character. After the supposed death of her son, Caleb, she locks herself in his room. Even Mildred, Isabelle’s closet friend, isn't allowed to see her. However, after Caleb’s surprise return, Isabelle grows a backbone. After some of the local women criticize George, her husband, Isabelle directly calls their values into question. Isabelle’s independence and self-reliance continue when George dies. She figures out how to manage the expansive property with the help of Mildred.

As Isabelle becomes more empowered, George seems to grow closer to her. At first, George and Isabelle’s relationship is depicted as cold and withdrawn. Isabelle shares her feelings with Mildred while George confides in a sex worker named Clementine. By the end of Nathan Harris's novel, George and Isabelle form a close bond. As George dies from the gunshot wound, Isabelle lovingly cares for him in their home.

Concerning Caleb, his character grows away from cowardliness and toward bravery. At the start of the story, Caleb is characterized as the opposite of courageous. He’s a shameful deserter who violently bullies by his best friend/sexual partner, August. Once August kills Landry, Caleb changes. He tells the truth about what happened in the woods and then frees Prentiss from the local jail.