Larkin's poem, "The North Ship," concerns the sailing of three ships. Each of the ships "goes sailing by" past the speaker of the poem. The poem depicts these ships as each undertaking qualitatively different journeys, experiencing success, hardship and suffering depending on the direction taken.
Starkly elemental and broadly (inscrutably) metaphorical, the poem portrays three different paths that may be taken and suggests that intentions and outcomes are intimately linked.
The style of the poem can be connected to imagism, a poetic trend of the early/mid 20th century that relied on specific images to convey meaning organically (i.e., without much exposition, if any).
In the poem, the speaker watches as the first ship heads west, "carried to a rich country." The second ship heads east "to anchor in captivity" and the third ship heads north.
The first two ships travel under a wind that is, respectively, helpful and violent. The third ship going north travels with no wind at all.
The third ship drove towards the north,
Over the sea, the darkening sea,
But no breath of wind came forth,
And the decks shone frostily.
The northbound ship, unlike the others, is "rigged for a long journey." It does not return, as the others do "happily or unhappily" but instead journeys "far and wide/into an unforgiving sea.