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)
The City Beneath the Sea - S1-E2
Continuity mistake: Seaview is on the ocean floor investigating the underwater city. Two inserted stock shots then show it up near the surface at periscope depth. In the next shot, though, it's back on the bottom again. (00:43:15)
No Way Out - S1-E12
Continuity mistake: When Victor tries to get into sickbay, the guard stops him, pointing a rifle at his chest. But in the very next reverse angle shot, the rifle is again in its original position in the guard's hands, pointing at the ceiling. (00:35:10)
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)
Continuity mistake: Captain Crane removes a failsafe key, which is hanging outside his uniform collar, from around his neck. It wasn't there in the previous shot. (00:10:30)