The poem is a short list of "uses," and each line gives a thing and its purpose. Water makes rain. Broth is for drinking. Those two feel practical and almost obvious, like entries in a dictionary. Then the list begins to drift. Love is "to fill up the afternoon," which treats love as something that occupies time, a warm way of passing an ordinary stretch of day. The last line is the strangest: the sea is "to be absent."
That ending changes how we read everything before it. The sea is huge and constantly present, yet here its use is to not be there. The speaker may be thinking of a sea that is missed, or of how an absence can shape a place or a feeling. The poem doesn't say, and that openness is part of its charm.
The mood is quiet, gentle and a little wistful. The speaker sounds calm, even content, but a thread of longing runs under the plain language, and the last line leaves us thinking about what is missing.