On the Island by Tracey Garvis Graves

When thirty-year-old English teacher Anna Emerson is offered a job tutoring T.J. Callahan at his family's summer rental in the Maldives, she accepts without hesitation; a working vacation on a tropical island trumps the library any day.

T.J. Callahan has no desire to leave town, not that anyone asked him. He's almost seventeen and if having cancer wasn't bad enough, now he has to spend his first summer in remission with his family—and a stack of overdue assignments—instead of his friends.

Anna and T.J. are en route to join T.J.'s family in the Maldives when the pilot of their seaplane suffers a fatal heart attack and crash-lands in the Indian Ocean. Adrift in shark-infested waters, their life jackets keep them afloat until they make it to the shore of an uninhabited island. Now Anna and T.J. just want to survive and they must work together to obtain water, food, fire, and shelter.

Their basic needs might be met but as the days turn to weeks, and then months, the castaways encounter plenty of other obstacles, including violent tropical storms, the many dangers lurking in the sea, and the possibility that T.J.'s cancer could return. As T.J. celebrates yet another birthday on the island, Anna begins to wonder if the biggest challenge of all might be living with a boy who is gradually becoming a man.