William Shatner is the uncredited narrator.
In one scene inside the submarine Scott Brady, Michael Dante and Jody McCrea discuss the operation and they use a map of the Mexican state of Baja California: it reads: "Mexico - Baja California, West Coast - Bahía de San Quintín".
Many of the underwater shots used stock footage from previous submarine movies like: "Destination Tokyo", "Up Periscope", and "Run Silent, Run Deep", which they themselves borrowed from each other.
The black and white film switches to color for two scenes: dream sequences featuring a song that Frankie Avalon sings with a group of young women. While the backgrounds and some of the women's gowns are in color, Avalon and the women themselves remain in black and white.
By this time submarine movies had pretty much maxed out on their plot lines, which all seem to present hard-bitten commanders, in conflict with their junior officers, and their naive and frustrated crewmen; with dreams of girlfriends left behind, and a perilous mission which they all must pull together to accomplish.