Someone has left the speaker, and the loss still fills every hour. The poem opens with a small, painful moment: the phone rings, the speaker hopes it's the person who left, and it isn't. That quiet disappointment sets the tone for everything that follows.
The main image is a boat on open water. The speaker tries to paddle toward shore and escape the thought of being left, but the boat has holes that are too big, so the effort feels doomed. Living itself feels heavy, as if the speaker's sense of purpose left along with the other person. By the end, the speaker drifts on "this water of never ending thoughts," wondering where the ex is and who they're with.
The sharpest pain comes in the last lines. The speaker imagines someone else doing what they feel they should have been doing: making this person happy. The mood is sad, tired, and full of regret, with a little self-blame mixed in with the longing.