In Lines 139-141, Eliot uses the image of the sea and "sea-girls," and the repetition of "singing," as well as the associations now accumulated around the word "overwhelming" (with its meanings of "submerging" and "engulfing") to symbolize the deeply emotional place which Prufrock could not reconcile with human life in the real world, thus necessitating the division in himself.
The Love Song of J. Alfred Prufrock