The opening stanza of "Shipwreck" portrays a ship battling for survival against a storm. It's not clear what ship this is, who is on board, or where and when the shipwreck takes place. As the speaker puts it, this is just the tale of a "little brig I knew." That vagueness gives the poem a mysterious quality, suggesting that the ship could represent something beyond itself.
A "brig" is a square-rigged sailing ship with two masts. It's not the biggest type of ship, but it's not small either! It's telling, then, that the speaker calls this boat "little," using delicate /ih/ assonance ("little brig") that sounds light and fragile. Set against the mighty power of the sea and the storm, the boat appears tiny and ineffectual. Humankind can build strong, powerful objects, this poem will suggest, but nature always maintains the upper hand.
Lines 3-5 further paint the scene. The ship is "O'ertook by blast"—in other words, overwhelmed by a ferocious storm. The speaker conjures the power of that storm through repetitions in lines 1 and 4:
It tossed and tossed,
[...]
It spun and spun,
The parallelism and diacope here make it clear that the ship has lost control—or, more accurately, that the crew has lost control of the ship, heightening an atmosphere of drama and chaos.
Overwhelmed by the storm, the speaker says, the ship "groped delirious for morn," desperately searching for a dawn it will never reach. This personification captures a very human feeling of helpless longing for safety: the groping ship starts to feel more and more like a symbol for humanity's struggles in the face of terrible troubles.
The rhythms of this stanza are unpredictable The meter is generally iambic (that is, it uses iambs, metrical feet with a da-DUM rhythm, as in "It tossed"). But the lines switch between dimeter (lines of two iambs, as in lines 1, 3, and 4), trimeter (lines of three iambs, as in line 2), and tetrameter (lines of five iambs, as in line 5). This lurching rhythm mirrors the turmoil of the storm. Like the ship, the poem is thrown this way and that, denied the chance to settle into a calmer flow.