Trivia, Quotes, Notes and Allusions
McCoy: What about you, Spock? What does your logic tell you?
Spock: The captain states the case emotionally, of course, but correctly. I would be of little value to this ship if I am confined to a tank in Sickbay.
Rila: The light is warm and the air is soft. I shall be glad when the surface places can be inhabited.
Domar: The young Aquans have decided to rebuild the great shelters of the air-breathers.
Kirk: Only the young Aquans?
Domar: Senior Aquans cannot adjust to the thought of becoming air-breathers. We will remain at the Aqua city.
Kirk: Don't lose contact with each other. Like your ancestors.
Domar: We will pass ordainments to forbid it.
Rila: And we this time will not ignore them.
Kirk: Look at this place - a tank! I can't command a ship from inside an aquarium!
George Takei and Nichelle Nichols are credited but do not appear.
James Doohan does seven voices in this episode!
First and last appearance of the aquashuttle, a specially-designed shuttlecraft designed to function underwater. As with much else is not considered canon, although the aquashuttle appeared in FASA's Star Trek Roleplaying Game (which is also considered non-canon).
The aquashuttle lands during the day. However, when Kirk calls Scotty for beam up, the sky behind him is a night sky.
When Kirk and Spock begin to explore the ruins of the old city, one shot shows Spock's uniform colored gold instead of blue.