Mike Belden, a troubled teen from New York City, is a guest of the Ricks. Mike's mother has just remarried and she and her new husband Sam Field are traveling. Mike believes his stepfather hates him. When the Fields arrive to take Mike home, Mike and Sandy go for one last scuba diving adventure.They become trapped in a sunken ship. Flipper leads Porter and the Fields to the site of the sunken ship. Porter wants to call the Coast Guard to rescue the boys but Mr. Field insists upon saving the boys himself. The boys are soon brought to safety. Mike is humbled when he realizes he owes his life to his stepfather.