Her enthusiasm for new thing and immediate immersion in details keeps the story optimistic. But the reader slowly learns that there are deeper issues hidden beneath the surface. Sophie was adopted at about the age of ten and no one will tell Cody what happened to her real parents. Uncles are supposed to be just uncles, but slowly these emerge as real individuals with overwhelming problems of their own. Cody, who refuses to be serious about anything, longs for his father's approval, but is unwilling to conform just for conformity's sake.
Clues abound in the text about the history of each individual, but nothing is clearly stated.
Creech is a master in the use of sub-text. As they sail, each person must teach the whole group something. Sophie's other cousin, Brian teaches them sailing terminology, while an uncle teaches radio code. Cody decides to beat Brian in learning the radio code first. Alpha, B is Bravo, C is Charlie, and so forth.