Factual error: Due to the extensive use of borrowed footage from the WWII film "The Enemy Below," the 1970s crew of the renegade sub (who are not German and who wore civilian clothes in most shots) suddenly acquire 1940s German U-boat caps and uniforms. (00:30:00)
Visible crew/equipment: The camera shadow is visible when the medical team removes the injured crewman on the stretcher.
Continuity mistake: The video set turns on before Admiral Nelson activates the "on" switch.
Continuity mistake: When the four divers exit the Seaview, each has a flashlight. When the reach their destination only three have flashlights.
Character mistake: Alicia sings the code to Crane and tells him he must remember it exactly the way she does it. He doesn't. He leaves out the extra "la la" before the last stanza. Astonishingly, Alicia says "perfect, now two of us know it." (00:01:05)
No Way Out - S1-E12
Factual error: Victor is crawling around through Seaview's incredibly roomy ventilation ducts, pursued by several crewmen. But the air conditioning that's fluttering little ribbons on all the vent covers isn't, for some reason, disturbing a hair on any of their heads. (00:44:25)
Continuity mistake: "11 Days to Zero": A saboteur on an overhead scaffold hastily sprays an X on the top of Nelson's car with white paint. In later aerial shots, the X is composed of 2 perfectly straight, thick lines stretching from corner to corner of the car's roof. No way was that X made in a few seconds with a spray can. (00:03:00)
Revealing mistake: One of the saboteurs sneaking into the palace keeps looking up at someone off camera. He's not watching the door he just entered by, so who's he looking at in what should be an empty corner of the room? (00:00:30)
Deliberate mistake: The huge system and missile control boards containing the failsafe units suddenly appear on Seaview's bulkheads just for this episode. And of course, they disappear after this, never to be seen again. (00:15:00)
The Cyborg - S2-E4
Continuity mistake: To expose The Cyborg duplicate of himself, Nelson disrupts the nerve controls on the computer facsimile's left hand. But The Cyborg Nelson's right hand is the one that subsequently malfunctions. (00:45:20)
Deliberate mistake: "The X-Factor": When the helicopter is chasing Nelson's car, re-used footage from a first season show briefly turns the otherwise color episode black and white. (00:24:00)
The City Beneath the Sea - S1-E2
Revealing mistake: On the beach, Molina is petite, thin and small-chested in her wetsuit. Underwater, she mysteriously gains several pounds, bigger muscles and a much larger bust, thanks to a poorly-matched stunt double. (00:12:00)
Continuity mistake: Throughout seasons 2-4: When the series went to color in the second season, the Seaview was redesigned with only one set of observation windows. But stock footage of the old multiple windows continued to appear for the rest of the series, usually with the film dyed blue.
Factual error: "Invaders": The ship's doctor claims that carbon 14 dating proves the man from the undersea capsule to be 20 million years old. Not likely. Carbon 14 testing can date once-living matter only within the last 70,000 years, and is generally considered accurate only within the last 50,000. (00:23:00)
No Way Out - S1-E12
Continuity mistake: When Anna tries to kill Koslow, Victor spies on her from behind the ventilation grate. The ribbons fluttering on the duct cover disappear when the shot switches to Victor's point of view. (00:46:50)
The City Beneath the Sea - S1-E2
Continuity mistake: Seaview's windows form 8 horizontal rectangles in 2 rows across its bow. But the interior sets have windows that form vertical rectangles, and they're much closer together than they are in the exterior shots. (00:02:30)
Continuity mistake: When a scuba diver (Pilar Seurat) approaches the flying sub, her regulator is on the left and her dive knife is on her right leg. Also, she activates the underwater voice transmitter with her left hand. Once aboard the flying sub, her regulator is on the right side, with the knife strapped to her left leg. Also, she's right-handed. The film of Seurat - more likely her stunt double - swimming towards the sub was likely "flipped".
The Wax Men - S3-E24
Revealing mistake: The heavy metal ring securing the hatch that leads from the flying sub to the Seaview control room bounces up and down as Crane enters the control room.
The Wax Men - S3-E24
Revealing mistake: The explosive squib is visible under the uniform of the wax Chip Morton right before Captain Crane shoots him.
The Wax Men - S3-E24
Continuity mistake: When Captain Crane is shooting the wax crew members, his pistol runs out of ammo, locking the slide open. The next shot shows Crane still shooting without reloading a new magazine.
