Writer:	Peter Packer, Peter Packer, Al Gail
Director:	Justus Addiss
Star:	David Hedison (Captain Crane),  Richard Basehart (Admiral Nelson)
Recurring Role:	Del Monroe (Kowalski),  Allan Hunt (Riley),  Robert Dowdell (Chip Morton)
Guest Star:	Peter Mark Richman (Gantt),  Barry Coe (Balter)

In the book Science Fiction Television Series, Sean Morgan states that he was cast for the role of sonarman at 6:30 in the morning that filming began. Casting director Joe D'Agosta had called him in a panic, having forgotten to cast the role. He was paid $500. Morgan later told D'Agosta he would have done it for scale ($180). (edit) There is a possible in-joke regarding the character Bill Balter, whose name combines the writing team of William (Bill) Woodfield and Allan Balter. (edit) The sea spider was also seen in the Lost In Space episode "The Keeper Part 2", where it looked less realistic than in this episode (which is saying a lot). (edit) Peter Mark Richman (billed in this episode without the "Peter"), is excellent as the obnoxious Gantt. He would return as Hendrix in "Secret of the Deep" in the fourth season. (edit) Richard Basehart is in only a few scenes shot in the Flying Sub. Mr. Basehart was hospitalized due to an ulcer and missed the remainder of this episode and the next two. Stu Riley's part was beefed up and a stand-in took over the physical aspects of the Nelson role. These scenes are easy to spot, as Basehart's voice is badly dubbed over the stand-in, who wears the Admiral's hat very badly. (edit)

Crane: The Admiral says Gantt's one of the most brilliant men he's ever known, but if you ask me, stability isn't his long suit.
Morton: Well, that's an understatement. (edit)

Uncredited roles:

Sean Morgan (Sonar), Wayne Heffley (Ship's Doctor), Ron Stein (Ray), Howard Curtis and Vince Deadrick (Crewmen)

This was Wayne Heffley's third outing as the ship's doctor. (edit)

This episode does not have any allusions. Add some now!