Abraham Lincoln is not just a vampire hunter. He's a standard and well-recognized hero for many Americans. In “O Captain! My Captain!,” the speaker has an intense amount of admiration for his captain, a stand-in for President Lincoln. Back on land, the people share in the speaker’s admiration and cheer the ship into the harbor. What the captain has done specifically to win everyone's admiration is never really made clear in the poem, but we do get the end results of his admirable actions: he's steered through rough seas and sacrificed his life to ensure the safety of the ship.
The sailor seems to admire the captain as though the captain was an ideal, masculine father, kind of an anti-Homer Simpson. He implies that the captain was stern but fair and emphasized hard work and success.
The speaker’s admiration for the captain is different from that of the people on shore. The speaker has witnessed the captain’s actions first-hand and has seen the captain overcome difficulties and errors that those landlubbers on land did not see.