Dave Bonta's "Seasick" is a single sentence, a single line: "He lies flat on the pitching deck among the humpbacks." Everything the poem does, it does in thirteen syllables, and most of the work is shared with the title. "Seasick" names the condition and the line shows only the body. We never read the word "nausea" or see anyone retch. We see a man horizontal on a moving floor, and the title lets us supply the misery ourselves.
The first thing to notice is the sentence's own movement. It begins with two heavy, nearly equal beats, "lies flat", and the line seems to settle with them. The man has stopped resisting. But the next phrase, "the pitching deck", brings the motion back, and the rest of the line rises and falls around his stillness. Even the sounds seem to lurch. Hard consonants pile up in "pitching", "deck" and "humpbacks": the p, the ch, the ck, the b and k. The line doesn't glide. It thuds, like a hull dropping off a swell. A short "a" links "flat" and "backs", one near the start of the pairing and one at the end, so that the sentence feels as if it has been pressed between two flat surfaces. There is no rhyme and no room for one. A rhyme would promise the neat return of an ear's expectation, and this poem is about a body that cannot get its balance back. The full stop at the end of the line is abrupt, like a door closing, though the sea of course carries on.
The real puzzle is the last word. "Humpbacks" could be whales, and it is hard not to picture them first, since the sea is the setting. But whales cannot be on a deck, and the grammar puts the humpbacks with him: he lies "on the pitching deck among" them. A reader has to choose, or decide not to. Perhaps the creatures are swells seen from a sailor's-eye view, rolling past like backs. Perhaps they are other passengers, hunched and curled over, equally ill. Or perhaps nausea has loosened the boundary between ship and ocean so far that the whales have, in his mind, come aboard. The poem doesn't settle this, and I think that is the point. Illness makes the world unreliable, and the line makes us feel that unreliability instead of explaining it.
There is also a quiet joke in the pairing of "flat" with "humpbacks". One word is as level as a board, the other is all curves and bulges. The man is flattened while everything around him heaves. Whales are creatures that belong to the sea and swim through its motion without complaint, so the man's collapse looks all the more human and all the more comic beside them. "Among" is a small, generous word here. It makes him one of the group, a body lying in a crowd of bodies, no longer the commander of the deck, only another large shape in the swell.
The choice of "He" matters too. The poem could have said "I", and the experience would have felt closer and sloppier, like a complaint. Instead the camera pulls back and the sufferer is seen from outside, a figure in a scene. That distance gives the line its dry humour. Seasickness is miserable, but it is also a little ridiculous, and the third person lets the poem hold both at once without begging for pity.
What makes "Seasick" worth reading is how much it trusts a reader. It gives one verb, one adjective that does double duty ("pitching" describes the deck but also suggests a throw or a toss), and one deliberately slippery noun. From those, the reader builds the whole voyage: the sky tilting, the whales or waves rolling by, the cold deck against a cheek. A one-line poem can't develop an idea, so it has to land one image exactly. This one does, and it leaves the reader slightly unsteady, which is just the right feeling for a poem about the sea.