The poem pictures a battered boat drifting through fog, and it reads like a quiet image of loss or aimlessness. The boat has torn rigging and a dislodged jib, so it can't steer properly. It moves from quay to quay but never finds a post to tie up to, and the tide carries it out again. The phrase "my broken bel étage" suggests the speaker is the damaged vessel, or at least that this is a picture of their own life or sense of self.
The speaker feels lonely, tired, and unmoored. The questions in the last stanza, about how far the water stretches and how heavy the harbor feels, sound weary rather than angry. By the end there is "no sail, no thread," so nothing is left to guide or hold the boat, and the fog simply waits. The mood is hushed, bleak, and a little eerie, with a sense of being stuck between arriving and disappearing.