Why in the world would the Gregory Peck character ...

The ending of this movie was always rather unclear.

In the book they take the sub out to the Bass Strait, in international waters, and sink it there. (Even then it's not clear whether they actually flood the sub and drown, or merely take her to the bottom and die there.)

But in the film it does sound as if they want to go back to the United States. The crew member tells the Captain, "We want to head for home." Whether that's an allegory for the afterlife, or a literal desire to return to their own country, is never really made plain. Later Towers (Peck) tells Moira (Gardner) that "The men kind of want to get home," then pauses and adds, "I can't explain it", meaning it's hard to put into words. That sounds like "going home" is a figurative phrase -- the men want to die aboard their sub. It's all very vague and uncertain.

One would also have to ask whether the men could even get the sub back to the States. It had the range and they had enough fuel and supplies, but by the time they were ready to leave they were mostly ill with radiation sickness. I don't think they could have gotten very far by that point. Like I said, it's unclear and confusing.

One thing in the film that is clear is that Towers does want to stay with Moira, but has to bow to his crew's wishes to leave. This is in sharp contrast with the book, where Dwight insists on doing his duty and staying with his ship. (He also has only ten men going with him, not enough to get back to the U.S. if they had wanted to.)

In the God-awful 2000 made-for-cable version, Towers basically deserts his crew even as they leave on the sub, just so he can selfishly die with Moira. A naval Commander running out on his command for personal convenience is a disgrace...even at the end of the world. One more mark against that dreadful, insulting and amazingly stupid movie.

In the film he does want to stay with Moira (Ava) but feels duty-bound to accede to his crew's wishes and "head for home". But as I said previously, what that means is very uncertain.

Every one of the crew was suffering from radiation sickness and couldn't possibly have made it back to the United States. (And where in the U.S.? A Pacific base like Honolulu or San Diego, or an east coast base like Norfolk or New London? That makes a huge difference.) Though the film is ambiguous at best, from the medical details alone it would have been impossible for the men to have literally returned to America, even at its nearest point.

Also, if you watch the men on the bridge as they go back inside the submarine near the finish, they very much look like men about to die, getting a final glance at the sky before sinking their sub just off the Australian coast in international waters. But the imprecision of the film is a bit annoying.

As I've said, all this is in direct contrast with the book, where Towers never intends to stay with Moira and makes this clear throughout. (He never even sleeps with her, because he wants to remain true to his late wife, while Peck and Gardner do finally become involved.) Also the book makes it plain that the small crew left on board (11, including Dwight) is not enough to go back to the States, and that that number is just sufficient for short runs, such as sailing into the Bass Strait. And there, most of the crew stays on shore. In the movie, while some are given leave to stay ashore, many appear to stay with the boat.

I like the fact that Dwight wants to stay with Moira but feels honor-bound to do his duty first. This is better than the novel, where Dwight's refusal to get involved with Moira seems a little too unrealistic, or the 2000 cable movie, where he happily and selfishly throws his duty and crew aside for his own crass reasons.

With no one left, and him the highest-ranking officer, he IS the United States. Additionally, the captain of a ship (or, in this case, boat) first has a responsibility to his ship, then his crew.

It's called "duty."

And it's easy to do one's duty when everything is going well, but the time it is best reflected is when everything has gone to hell. Then, duty is the indication of the strength, decency, and courage of a man.

Do you not get that?

..Joe