Lieutenant Braden discovers that Sally, the woman he's been falling in love with, has actually been checking out his qualifications to be a U.S. Navy frogman. He must put his personal life behind him after being assigned to be smuggled into a Japanese-held island via submarine to photograph radio codes.

The new commander of a Navy Underwater Demolition Team--nicknamed "Frogmen"--must earn the respect of the men in his unit, who are still grieving over the death of their former commander and resentful of the new one.

The Mediterranean, 1941/42 - Axis forces are using frogmen and manned torpedoes to attack previously impregnable harbours. The Allied forces need to come up with something to answer this threat, which they find in the form of Lt. Lionel "Buster" Crabb.

In an alternate timeline, Ken, Lobang and Wayang King are transferred to the Naval Diving Unit (NDU) and have to overcome obstacles and personal issues to grow as people.

One of the first ‘frogmen’ in the Navy Reserve fights to survive missions behind enemy lines and his own capture at the Mauthausen concentration camp.