Twelve-year-old Julie Sims prepares for a scuba dive off the coast of Gulf Shores, Alabama in her father’s boat, the Barbie Doll. Her dad, Gibson Sims, is a diving guide and has just found the location of a pair of abandoned army tanks, called the Malzon tanks, on which an artificial reef formed. As the only person with the coordinates to the tanks, Gibson is in an ideal position to make money by taking divers to the otherwise unknown and untouched reef, and Julie knows he needs money to pay bills and keep his dive shop and charter business open. Today will be Julie’s first dive to see the tanks, and she will also assist her father as a guide.

Two wealthy clients, Hank Jordan and his son Shane, paid handsomely to explore and fish at the tanks. The Jordans are argumentative, rude, and ignore Mr. Sims’s diving advice, but Julie knows her family needs the money these clients are paying. She remembers Shane from elementary school but does not have a positive impression of him. As Gibson maneuvers the boat into place at the dive site, Julie notices that his diabetes might be affecting him.