Sentence:  This is the answer to the choice of the man who does not choose: now he does indeed have the sea, he plunges into it headlong, swaying among the corals of the depths, "Hanged" by his feet in the <WSD>sargassoes</WSD> that hover half-submerged beneath the ocean's opaque surface, and his green seaweed hair brushes the steep ocean beds. 
Meaning of the word marked with <WSD> tags:  A brown alga, of the genus "Sargassum", that forms large, floating masses.