Whitman calls his poem "a rude brief recitative," and the phrase works like a set of reading instructions. A recitative is sung speech, closer to talking than to a tune, and "rude" promises roughness over polish. That is what the poem delivers: no rhyme, no steady metre, only lines that stretch and shrink the way water does. The first section is built from a string of "Of…" phrases: "Of ships sailing the Seas," "Of unnamed heroes," "Of waves spreading and spreading," "Of dashing spray." Each one arrives like another swell, and Whitman admits as much when he calls his chant "Fitful, like a surge." The doubled "spreading and spreading" does what a single word couldn't, because the horizon seems to keep retreating as we read.
The sea here is more than scenery. It becomes a person with a purpose, the one who "pickest and cullest the race," choosing its sailors "sparingly, without noise." "Cull" is a farmer's verb, and the poem follows it up. In the bracketed lines the chosen few are "enough for seed preserv'd," as if courage were a crop that must never die out. Then the sea turns into a mother, an "old husky Nurse." "Husky" is a clever choice, since it suggests hoarse, rough and strong all at once. This nurse is not gentle, and her children grow up "Indomitable, untamed as thee," so what she feeds them is her own wildness.
Look at who these heroes are: "unnamed," "taciturn," people "whom fate can never surprise, nor death dismay." A poem this loud in its rhythms is celebrating people who make no noise. The parenthesis even steps ashore, where heroes appear "on water or on land, by ones or twos." The sea becomes a measuring stick for courage anywhere.
The second section changes mood. The list of "Of…" phrases gives way to commands, and Whitman speaks straight to the ocean: "Flaunt out O Sea, your separate flags of nations!" He doesn't wipe out national differences. The flags may fly "visible as ever." But he wants one more banner, "one flag above all the rest," and this one is made of no cloth. It is "A spiritual woven Signal," "twined from all intrepid captains, young or old." The craft verbs "woven" and "twined" are physical, yet the thread is human lives. This answers the first section's claim that the sea "unitest Nations": the ocean joins countries together, and the flag is the sign of that joining.
The flag also remembers the dead, "all that went down doing their duty." "Went down" is plain, almost understated, and it carries a double meaning. Ships sink, and so do the people on them. Against that downward motion Whitman sets an upward one, calling the flag an "emblem of man elate above death." "Elate" means lifted up, so the dead lie below the waves while their signal flies above. The flag is "subtly waving," barely noticeable, and that suits the quiet heroes it honours. It does not shout.
The final line, "All seas, all ships," repeats the title, so the poem ends where it began, the way a tide returns. The repeated "all" matters too. The poem is a song for everyone, with no nation, rank or famous name left out.
That inclusiveness is the poem's main significance. Whitman writes in the long, unrhymed free verse he is known for, and here the form matches the subject: loose, rolling lines for a loose, rolling sea, with nothing neat or caged. The idea at its centre is democratic. A monument usually goes to a general or a king, but here the honour goes to the "unnamed," and the emblem belongs to no country. The poem asks what a flag would look like if it stood for courage itself and not for territory. Its answer is a flag that flies over every sea and is made of the people who sailed them.