The speaker walks into the sea with one purpose: to talk to the dead. That is a striking idea, and the poem barely explains it. The title, "Full fathom five," echoes a line from Shakespeare's *The Tempest*, where a drowned father is imagined lying five fathoms deep. That connection suggests the sea as a place where the dead rest, though the poem itself never says who these dead are.
What the speaker feels is packed into the last two words: "loving" and "raging." They sit alone on their own lines, with no punctuation and no explanation, as if the speaker can't choose between them. Grief often works this way. You can miss someone tenderly and be furious that they're gone, both in the same breath.
The mood is hushed, heavy and a little dangerous. The short lines leave a lot of white space, like the silence of deep water. Because the speaker "entered" the sea rather than just visiting its edge, we sense a willingness to go under, to meet the dead on their own ground.