Here's why:
* Literal Impossibility: Fish cannot survive out of water. The image is inherently absurd and illogical, symbolizing something that cannot be.
* Sal's Journey: Throughout the novel, Sal experiences many confusing and upsetting events, such as her mother's disappearance, her grandmother's eccentricities, and the hardships faced by her friends. These experiences feel like "fishes in the air" – things that don't make sense and are difficult to comprehend.
* Sal's Dreams: Sal's dreams often involve bizarre and surreal imagery, further emphasizing the sense of the impossible.
* Grandma's Wisdom: Sal's grandmother uses the phrase to teach Sal that life is full of unexpected and sometimes painful experiences, and it's important to be open to the unknown.
The "fishes in the air" metaphor reflects the challenges and uncertainties of life that Sal encounters, prompting her to question her reality and search for meaning.