I was rather surprised at the violence of the opening, with poor Captain Phillips biting the dust with a clearly seen shot to the head. In the future, a great many people would get shot with nary a mark to show for it.
It seemed as though the writer of the episode was deliberately trying to make it seem as though Dr. Wilson was actually an enemy agent. When Lee Crane's name is put forward as a replacement captain, Wilson disagrees, claiming that Crane is too unimaginative for the job. At dockside, Crane cheerfully greets Wilson, only to have Wilson give a curt answer and hurry past him. It is clear from Crane's expression that he has no idea why Wilson is so hostile, and no explanation is ever given. When the unknown enemy begins dropping depth charges, Wilson reacts oddly, merely glancing upward with a "O.K, here we go" look. When a vital chunk of equipment is ripped off the hull, Wilson is quick to suggest that the mission be scrubbed. When he unexpectedly volunteered to go out with the divers, I really thought that he was trying to further sabotage matters. It was not until he helped save Crane (and recovered the missing equipment) that it became clear that, yes, he's one of the good guys.
They added more tension to the show with Crane's first, stealthy entrance to the Seaview, and his subsequent "warm" greeting by the crew--that was not warm enough. The crew was not told the details of the mission which didn't help their initial resentment of the new captain, but it didn't take long for both captain and crew to realize the other's true worth.
Threat piled on threat, building up to an exciting and satisfying climax--in the very nick of time, of course. According to the bonus section on my DVD, when this pilot was shown to the T.V. executives, they gave it a rare round of applause. I'm not surprised.