What does Blue 55 represent?

Blue 55 symbolizes Iris's difficulties in navigating the world as a Deaf person among her non-Deaf family members and classmates. Blue 55 is a whale whose song is at a different frequency than that of other whales, leaving him unable to communicate with anyone else and abandoned by his family, who view him as a threat to their survival. Iris connects with him so heavily because she recognizes similarities to her own life, especially with a family who does not naturally speak her language and classmates that try but ultimately fail to understand and be understood by her.