The X on top of Admiral Nelson's car increases in size from when it is first painted on.
During the torpedo attack, the captain orders the crew to their battle-stations. However, the first torpedo hit is followed by a shot of men gathered around tables in the mess hall.
An earth tremor jolts the submarine causing water to splash over Kowalski and another sailor. Kowalski is soaked all along the front of his body from the top of his shoulders to his knees. As the scene's angle shots change, both of the men's shirts vary from just damp to very wet. Eventually, an over-the-shoulder shot from the back of Kowalski reveals that his shirt is completely dry and well pressed.
After the explosion on the polar ice, the Seaview dives to avoid the ice that is falling to the bottom of the sea. The ice may with some gravity break the surface of the water and sink a little, but it would float back to the top, and not continue sinking.
Three divers in standard wet suits leave the sub even when it is supposedly at a depth of 1000 feet. They would be crushed at that depth.
Admiral Nelson sleeve strips is that of a full admiral (four stars) yet his collar insignia is three stars, a vice admiral.
In the first episode they know when two earthquakes will happen and even the magnitude days before they happen and the quakes happen to the second of when they are predicted. There is no way to accurately predict earthquakes.
During the Arctic scenes wrinkles and/or seams can be seen in the "sky".
When Captain Crane is looking through the periscope during Seaview's first dive, the bow shown is of a old World War II vintage submarine.
Even though they are under the Arctic ice, all the fish they see are warm water fish.