In the first stanza of the poem, Whitman uses a metaphor—a comparison of two unalike things where one is said to be the other—referring to the United States as a ship. He says that the "ship has weather'd every rack, the prize we sought is won," meaning that the ship (the country) has survived lots of storms (most recently, the American Civil War, between the North and the South), and the Civil War has been won by the Union (the North), so the country will remain as one. President Abraham Lincoln was the captain of this ship, and so the poem is addressed directly to him. When the speaker refers to "the vessel grim and daring," he is referring to the ship, the metaphor for the United States. It is a vessel because it is a ship; it is grim because the war has just ended and a great many lives have been lost in the fighting; and it is daring because the country has dared much—I think of the American Revolution and how the colonies stood up to the British Empire and won. The speaker goes on to discuss the blood on the "deck" of this ship because Lincoln is dead; he was shot in the head by John Wilkes Booth while he attended the theater one night in 1865.