Coleridge speaks to a stream as if it were an old friend: "Dear native Brook! wild Streamlet of the West!" The title names it as the River Otter, which runs by Ottery St Mary, the Devon town where Coleridge was born, so "native" means just what it says. The poem works without that fact, though. Its subject is how stubbornly childhood scenes survive in an adult mind. Years have passed, "happy" and "mournful", yet the speaker has only to close his eyes in the sunlight and the whole riverbank comes back. The poem ends in a sigh of longing: "Ah! that once more I were a careless Child!"
The central contrast sits in the opening lines. As a boy he "skimm'd the smooth thin stone along thy breast, / Numbering its light leaps." The stone touches the surface, bounces and is gone, which is a fair picture of childhood play. Memory behaves in the opposite way: "so deep imprest / Sink the sweet scenes of childhood". The stone skips and the scenes sink. The poem then reverses the movement once more, because when the speaker shuts his eyes, "straight with all their tints thy waters rise." What went down comes up again. The inverted word order in "Sink the sweet scenes" even makes the sentence drop its verb into the middle of the line, as if it were sinking too.
The remembered details are small and physical: "thy crossing plank, thy marge with willows grey, / And bedded sand that vein'd with various dyes / Gleam'd through thy bright transparence." There are no people in this picture and no dramatic events, only a footbridge, a grey fringe of willows and coloured sand seen through clear water. The memory is a landscape the child once stood inside. The word "various" appears twice, first for the "various-fated years" of adult life and later for the "various dyes" of the sand. The adult's years are mixed and unpredictable, while the river-bed's variety is bright and clear. "Transparence" sums up the contrast, since the child saw straight through to the bottom and the grown man cannot see through his own years.
The form is a fourteen-line sonnet in iambic pentameter, but the rhyme scheme doesn't follow a standard pattern. It runs roughly ABBAA CDCDCD ECE. The opening five lines lean on a single pair of sounds (West, past, last, breast, imprest), which gives the start a tight, almost chiming feel. After that, the rhymes eyes, rise, dyes and sighs form a quiet chain: seeing, rising, colour, sighing. The ending ties "beguil'd" to "Child", so the rhyme itself says that the visions charm and trick him because they are visions of childhood. Enjambment keeps the sentences spilling over line-ends ("since last / I skimm'd", "mine eyes / I never shut"), so the thought runs on with the feeling of someone who cannot stop remembering.
The turn comes at "On my way", when the poem leaves the river and looks at the speaker's present. He addresses a second listener, "Visions of Childhood!", who "oft have ye beguil'd / Lone manhood's cares, yet waking fondest sighs". "Beguil'd" can mean both to charm and to distract, and the line admits that the comfort has a cost. The same visions that ease his cares also wake his sadness. "Lone" suggests that adulthood feels isolated, and the final line picks up the word "cares" in "careless". To be a child, in this poem, is to be free of care in both senses, without worry and without knowing what will be lost. Judging by that last wish, the speaker feels the loss most strongly now.
The poem is significant because it packs a large, lasting subject into a small space. Childhood memory, the pull of a place and the ache of time passing are all gathered around one stream and one thrown stone. It also shows how Coleridge, a Romantic poet, could treat feeling as something you see before you name it. The sadness is carried by willows, sand and sunlight, and only in the last line does it become a plain statement. By then, the reader has already crossed the plank and looked down through the water.