In section 33 of "Song of Myself," how is the skipper of the boat depicted?

You are referring to the skipper who rescues passengers off the drifting wreck of a steamship. The skipper is portrayed as a courageous hero:

I understand the large hearts of heroes,
The courage of present times and all times,
How the skipper saw the crowded and rudderless wreck of the steamship, and Death chasing it up and down the storm,
How he knuckled tight and gave not back an inch, and was faithful of days and faithful of nights,
And chalk'd in large letters on a board, Be of good cheer, we will not desert you;
How he follow'd with them and tack'd with them three days and would not give it up,
How he saved the drifting company at last,
How the lank loose-gown'd women look'd when boated from the side of their prepared graves,
How the silent old-faced infants and the lifted sick, and the sharp-lipp'd unshaved men;
All this I swallow, it tastes good, I like it well, it becomes mine,
I am the man, I suffer'd, I was there.

The skipper’s courage is expressed through his care for the victims on the wreck and through his determination to save them. His message to them—“We will not desert you”—is a promise he keeps against all costs, following the wreck for “three days and would not give up.” There is also a sense, not unintentional, I think, in which the skipper’s promise to the victims is like a promise made between lovers: the skipper was, as Whitman says, “faithful of days and faithful of nights.” If you think about the skipper as a lover, and his rescue of the victims an expression of that love, then I think you begin to have a clue about Whitman’s relationship to this little story and what the secret of “Space and Time” (from the very beginning of the section) might be. In this section, Whitman begins to understand the universality of his poetic impulse; the secret that he guessed (“now I see it is true, what I guess'd at, / What I guess'd when I loaf'd on the grass”) is that through his poetic sensibility he transcends the limits of space and time, and is, in effect, omnipresent (“I am afoot with my vision,” he says).

This explains the odd sense of detachment there is in the way Whitman handles the story of the skipper. He is a hero, but his story is less a story of how his bravery saved people from certain death and more an example of the essential universality of the poetic impulse. The skipper does “save the drifting company at last,” but the triumph is Whitman’s: “All this I swallow, it tastes good, I like it well, it becomes mine.” The skipper’s heroism is merged with Whitman’s poetic spirit; the triumph, ultimately, is the triumph of Whitman’s poetic ambition.