In The Great Gatsby, the last sentence reads:
So we beat on, boats against the current, borne back ceaselessly into the past.
This refers to the dualities of Gatsby and America.
At the end of the novel, Nick aligns himself Gatsby. Nick says Gatsby is worth the whole damn bunch (the Buchanans and Jordan, et al) put together. So, Nick is saying he will get into Gatsby's boat, the one that only sailed backwards on the sea of history--into the past to recapture his childhood dreams. Why do you think Nick goes back to his home, the Midwest and narrates the entire novel from there? It's an idealistic, quixotic quest--both Romantic and hopeless.
Gatsby looked like a Romantic hero to Nick: he was a self-made man, a rags to riches story, a symbol of the American dream. But, when Nick get close enough, he saw that Gatsby was illegitimate. Nick found out that Gatsby used any means necessary to try to repeat the past.
Earlier, Nick paraphrases Gatsby's story of falling in love, perhaps for the first time, and the last time, when he met Daisy. Since then, Gatsby admits, his life has been disoriented. This is obviously before World War I, when he (and America) was young, boyish, innocent, idealistic, and romantic.
Gatsby is symbolic of America: his innocence in America's. Daisy is symbolic of his past. His longing to return to his past is akin to the Lost Generation wanting to recapture their lost boyhoods. Since then, they've lost their identities over on the battlefields of Europe, while rich kids (Tom) stole their girls (Daisy) back home.
I do not think it means death. To me, it is Fitzgerald's commentary on the meaning of the novel.
Your question says to look back at the previous three paragraphs. To me, those paragraphs are about how, in the past, it was more possible to dream big dreams (like the Dutch sailors did). But now, the world that those Dutch sailors saw has gone. Its trees have been cut down to make way for things like Gatsby's house.
We, as people, are forced to try to get back to this past. Our humanity makes us want to go back to a time when dreams were possible. The problem is that we really can't get there.
In The Great Gatsby, the final line of the novel echoes what Gatsby does throughout the novel, as well as what he was doing in the five years preceding the opening of the narrative: trying to recapture the past.
In the paragraphs leading to the final line, Gatsby metaphorically compares the wonder felt by discoverers seeing a continent for the first time, with Gatsby's wonder seeing Daisy's home in the distance for the first time. At that moment Gatsby would have been closer to his dream than he had been for five years. He would have felt that he was almost there, almost arrived, so to speak.
Specifically, in the final line, Nick compares men rowing in wonder toward a discovered land, to Gatsby, specifically, and all people, generally, struggling endlessly toward a past that he and we want to recapture. And notice that the struggle is carried on "ceaselessly." It is a winless struggle.