The poem starts from the old saying about casting your bread on the waters, which promises that a good deed will come back to you. Here, nothing does. The speaker sends something out and waits, and the poem turns into a strange, half-comic interview, with one voice asking questions and another answering them. The bread becomes a stand-in for whatever the speaker has lost or given away. It might be a person, a hope, or a message that never got an answer.
The feeling is a mix of longing and stubborn dryness. The speaker drinks homemade tea, whistles at a steam grate, and licks their glasses clean, small lonely acts that show how long the waiting has gone on. The images keep shifting too: the bread is a failed boat, then something like a lung, then just dates on a calendar. The last line is the sharpest. If the bread ever returns, the speaker will "teach it to sink," a flash of hurt and anger under the calm.