The poem starts with an idea about generosity: giving, as the speaker understands the poet Akhmatova to mean it, without expecting anything back. The title suggests the poem is in conversation with her, though the text itself doesn't say more than that. From there it shrinks the idea down. Not even a reply is asked for. A single line would be enough, offered almost like an emergency measure, the way you might send up a flare.
Then comes the image of the message in a bottle, introduced casually, with the aside "you know." It's a familiar picture, and the speaker knows it. The last line changes the tone: "How quiet, sometimes, the sea." Here the speaker seems to admit what generous giving can cost. Nobody answers. The mood is gentle and a little lonely, resigned but not bitter. Writing, the poem suggests, means sending words out and learning to live with the silence that follows.