The episode has a rather serious continuity problem. In Doomsday
, just a few episodes earlier, no fewer than four men had to turn keys simultaneously to arm Seaview's nuclear missiles, and this could only happen after the President authorized their firing by opening a control access window. Indeed, a great hazard to the ship required the president to briefly reopen that window, risking the launch of any missile, anywhere! Yet here, Logan's prize crew is apparently able to arm and fire the missiles with just one man operating a few switches. A nuclear device contains a considerable amount of conventional explosive, and perhaps Logan believed this would be sufficient to achieve his goal - but nuclear weapons have always possessed many safeguards ensuring they will not detonate due to mischance of any sort. We never see Logan or his men disable these or hear them comment that they have done so. Even worse, Seaview
carries conventional torpedoes, the usual weapon a submarine deploys to deal with hostile craft. These would have been sufficient to the task Logan intended for the nuclear missiles.
Nelson claims submerging while men are on the submarine's deck will kill them. This seems unlikely while the boat is docked (as it then was); the men would simply enter the water feet from dry land. Possibly a poor swimmer would succumb, but there were enough men there to rescue any individual like that. At sea, with no ships around and no intention of returning, it would be a different story.