The title promises a sailor's wisdom, and the first line sounds like a command: "Boy in the bay, stay." The rhyme of "bay" and "stay" is the only true end-rhyme in the poem, and it lands at the very start, like a hand on the boy's shoulder. What follows is the lesson he is told to "understand": "letters only attend / the coming of a sail." Letters can mean mail, news carried by ships, but also learning itself. The verb "attend" suits both. Letters wait on the sail like servants, and "attend" also means "pay attention," which echoes "understand" just above it. Knowledge, the sailor says, will come to the harbour if you let it.
The middle four lines turn from advice to confession. "Midway, we could see / places very pleasant; / the further we went, / the more we lost sight." The language is almost deliberately flat. "Very pleasant" is the kind of phrase a tired traveller might use, and the plainness makes the loss sharper. The paradox is neat: going farther should mean seeing more, but here it means seeing less. The pleasant places belong to the halfway point, and pressing on costs the voyagers both them and, perhaps, the shore they left. Notice, too, that the pronoun has changed from the commanding address to the boy to a collective "we," and the verbs have slipped into the past tense. The sailor now speaks from memory.
The last four lines shift again, this time to a card table, with no explanation. The "I" is singular now, and the tense returns to the present: "At cards, I come to see / my fruitless precaution." The word "see" repeats from line five, so that seeing, which was lost at sea, is partly recovered in a small, rueful insight. "Precaution" is the longest, most formal word in the poem, and the sailor places it at the end of a line only to call it "fruitless." The closing couplet-like pair, "getting without book / when I can get the book," plays on an old idiom: to know something "without book" is to know it by memory. The sailor has been collecting experience by heart, the hard way, when the real "book" was within reach. In some card games "book" is also a term for a set of tricks, which would let the image work at the table as well, though the poem never insists on this.
Formally, the poem is spare. It has twelve lines with no stanza breaks, but the sense falls into three groups of four: advice, voyage, cards. Most lines run to about five syllables, which gives the voice a clipped, proverbial tone, like something muttered rather than declaimed. Nearly every word is short and ordinary. The few longer ones ("understand," "attend," "pleasant," "precaution") stand out like landmarks. Sound ties the lines together more quietly than rhyme does: "understand" and "attend" share their closing consonants, and "book" is repeated at the very end, so the poem finishes on the same word twice.
What makes the poem interesting is that its advice is not as simple as it seems. On one reading, the sailor's regret supports the opening command: stay in the bay, because books and letters will reach you anyway and the voyage only blurs your vision. On another, the line about "fruitless precaution" turns against caution itself. Perhaps the sailor's real mistake was hedging and playing safe, and the boy is being warned about that too. The poem does not settle the matter. It leaves the reader holding a piece of advice that has been quietly undercut by the person giving it, which is probably how most real advice works. In twelve short lines it asks whether we learn more by going out into the world or by waiting for the world to arrive, and it lets the speaker be unsure of the answer.