Two people have come to visit, but they have run out of things to say. That's the quiet at the centre of this short poem. Instead of talking, the speaker turns to the landscape outside, and the land starts to feel like a third presence, something that keeps them company when conversation can't.
The last two lines are harder to pin down. "Her house on the sand" suggests the cottage belongs to someone else, and sand hints at something fragile or temporary. The idea that the house "will make / little use of it" seems to mean the house, or the woman in it, can't do much with that company or that closeness. The poem doesn't spell this out, so it's open to interpretation.
The mood is hushed and a little melancholy. There's an awkwardness between people, but also a kind of acceptance. The speaker doesn't seem panicked by the silence. The sea and shore simply take over where words leave off.