This poem tells of an old god-like man who has risen from the sea. The speaker speaks directly to him as he rises from the cold, foamy ocean tide.
The poem begins with the speaker's observations. The man, white-haired and bearded, rises and falls with the waves as they "crest and trough." His knotty, wrinkled hair floats out for miles; within them are the "old myths of origins / Unimaginable." She compares him to the ice-mountains, which one must avoid and can never fully fathom. She considers his obscurity to be proof of his many dangerous qualities.
The speaker is unable to look at him much, but she does recognize that he seems strangely injured as he fades away while the vapors disintegrate over the sea. She has heard rumors of his burial, but realizes they are false since she sees him here. In the lines of his face lies evidence of many ages. She believes that his humor and endurance can withstand the earth and the sky.
Below his waist, he is a "labyrinthine tangle" rooted deeply among bones. She describes him as "inscrutable," since people lose their heads when they see him. The old man is able to defy both "questions" and other gods.
The speaker considers herself exiled from his kingdom as she walks on its borders. She implies a past connection with him, noting that she remembers his "shelled bed." She calls him "Father" as she breathes the thick, murderous air of exile. She ends the poem by saying she would "breathe water" instead.
"Full Fathom Five," a poem usually considered to be about Plath's father (Otto Plath) and thus studied alongside "Daddy," "Lady Lazarus," and "The Colossus," is dated from 1958 and was included in Plath's first published collection of poetry, The Colossus. It references Shakespeare's The Tempest, particularly a song sung by Ariel, the sprite controlled by magician Prospero. In her song, Ariel sings, "Full fathom five thy father lies; / Of his bones are coral made; / Those are pearls that were his eyes: / Nothing of him that doth fade, / But doth suffer a sea-change / Into something rich and strange." In the context of the play, the song is about Ferdinand, who lost his father Alonso in a shipwreck and spends the play looking for him on the shore.
In the poem, Plath configures her father as a Poseidon/Neptune figure of such immense proportions that he cannot be grasped by the eyes or mind. She describes his beard as being "far-flung" and his hair as being "miles long;" he is as large as the "ice-mountains," and is "inscrutable." His immensity is only matched in degree by his age, reflected in the "archaic trenched lines" of his face. He is not simply a god, but rather defies godhood. Clearly, she has taken great pains to emphasize his colossal figure and magnificence, which speaks to the immensity her father's memory had in her mind. He is too large for her to even fathom or understand.
Plath's tone is one of awe and wonder at her father's vastness, but also at his danger. She reveres him without losing sight of his dangerous potential. Everything about his setting - the limitless waves - is a threat to the human, limited speaker. However, though he and his watery life are dangerous, she admits she would "breathe water" in order to join him. Moreso than in "Daddy" or "The Colossus," her sense of admiration and love for him permeates this poem. But like those poems, the figure of her father presents a threat as well.
In fact, Plath's style of writing in this poem reflects her ambivalence toward her subject. While some critics have discerned a tone of awe or great love, John Ramazani sees a menace in the figure that is manifested in her "coldly formal tone, diction, and syntax, nearly freezing the poem's momentum with clotted alliterations and impeded rhythms. Her glacial language is an apotropaic mimesis of the father, who is as 'cold' as 'ice-mountains // Of the north, to be steered clear of / Of, not fathomed.'" The tone is impassive and stoic, suggesting a level of resentment and emotional distance.
However, her ambivalence might actually be what keeps him alive in her memory. Ramazani also suggests that the final lines imply incest, with their allusions to a "shelled bed" and the speaker's exile. This does not have to be taken as literal incest, however. This sense of ambivalence and abuse certainly conforms to her feelings about the patriarchal literary world. The idea of "exile" also resonates in this interpretation. As she often does, Plath connects her biography to more universal ideas, although in a way that does not fully elucidate either interpretation, but instead confounds them both in profound ways. Regardless of how one understands the figure, Plath's ambivalence - her desire to see him but her resentment over "exile" - is what reads most powerfully and defines him for the reader.
Finally, some biographical information provides insight into the poem. Plath was exceedingly fond of the sea, both in life and in her art. She spent her youth vacationing on the North Atlantic coast, so that the setting became associated with her father. She wrote of her experiences with the sea in "Ocean 1212-W," ending it with this reflection on that time: "And this is how it stiffens, my vision of that seaside childhood. My father died, we moved inland. Whereon those nine first years of my life sealed themselves off like a ship in a bottle—beautiful, inaccessible, obsolete, a fine, white flying myth." This connection helps to understand both why she fashioned her father as a sea god and why the setting is so emotional and impossible. The sea, as reflected in her remembrance, is a place of nostalgia for a distant past. She cannot return to it, but instead can only observe it from afar, when memory allows.