Carl Brashear (CUBA GOODING JR.) is the son of a black Kentucky sharecropper who's determined to make something of his life. A longtime underwater diving fan, Carl enlists in the Navy, hoping to become a diver, but finds himself stuck in the galley due to the racial restrictions of both the time and the institution.
A lucky break and a compassionate officer, Capt. Pullman (POWERS BOOTHE), get Carl reassigned as a seaman on a search and rescue ship where he first encounters Billy Sunday (ROBERT DE NIRO), a Master Chief Diver who risks his life, and disobeys direct orders, in an attempt to save another man's life. As a result, Sunday evokes the wrath of his superior officer, Hanks (DAVID CONRAD), and finds his diving career finished due to medical complications.
Two years later, Sunday is the instructor at the U.S. Navy Dive and Salvage School in New Jersey that's run by Mr. Pappy (HAL HOLBROOK), a one-time Navy star whose mental instability led to his current post. Sunday's none too happy about the hand life has dealt him. His marriage to Gwen (CHARLIZE THERON) is rocky due to their drinking problems and his continual resentment of no longer being a diver, so he often takes out his frustrations on his students.
One of them is Carl, who, with a recommendation from Pullman, enrolls in Sunday's school, only to find racist attitudes from him, Pappy and most of the other students, including Rourke (HOLT McCALLANY). His only friend turns out to be Snowhill (MICHAEL RAPAPORT), a stuttering student who rubs Sunday the wrong way.
Although he works hard to graduate, Carl learns that his academic grades might keep him back, so he enlists the tutoring aide of Jo (AUNJANUE ELLIS), a pre-med student and the romantic sparks immediately fly between them. With his grades improving, Carl sets out to prove himself in both training school and beyond, and must then overcome various obstacles along the path to his goal of becoming a Master Chief Navy Diver.