Always a master of language, Napoli's prose offers much imagery. Early on readers are told of Sirena's fascination with the "cunning squid, who are transported in bliss when they shot up into the air, letting off an internal light." The reader feels Sirena's passion at the squid's rush of what seems to be emotion, an emotion she shares as she strives to be as free.

The passages that describe her swim toward a pod of frolicking porpoises—her play with them as she indulges her fish persona, playful, mischievous, familiar— evoke her loneliness without her sisters, her school. When she witnesses the porpoise birth and rises with them to push their baby to the surface for its first breath of air, the reader will imagine Sirena's own body straining to give new life—something that will always be impossible for her.

Sirena is...