The first episode, "The Human Bomb", and episode 2.7 (12/18/52) ".22 Rifle for Christmas" are the only episodes of the original Dragnet that are not titled "The Big..." something.
The series opener ran in real time, and it contained several clock-on-the-wall shots to keep track of time. The story starts with the police frantically trying to meet a 26-minute deadline to satisfy the demands of a terrorist. The show ran for 26 minutes, excluding commercials.
Raymond Burr here is Deputy Chief Thad Brown; in the radio version he'd played Brown's predecessor as LAPD Chief Of Detectives, Ed Backstrand.
Putting a bomb in water will make the electrical connection complete and set off the bomb not stop the bomb.