This episode marks the first appearance of Morris O'Brian, who becomes a regular cast member in the following season.
This episode has the longest act of any episode with the first act clocking in at nearly 22 mins.
The filming of the submarine took place aboard nuclear submarine USS Topeka homeported at Point Loma Naval Base, San Diego for two days. Crew members of the submarine, including Kingsley Van Duzer and Mark Szymanski, appeared as Russian and US Navy personnel.