What Sophocles heard, according to the poem's speaker, was an "eternal note of sadness" in the sound of the sea. The words "ebb and flow" are used figuratively to refer to "human misery," but this figurative meaning is closely tied to the literal image of the tide's movements, as the speaker repeatedly links a feeling of sadness to the sound of the sea.

The term "ebb and flow" literally refers to the movement of the tides. The ebb tide draws the water away from the shore towards the low water mark, while the flow tide flings it back and makes the water rise. This metaphor expresses the idea that while there is always sadness in human life, the magnitude of this sadness falls and rises over time.

In his prose writings, Arnold developed a cultural theory in which he held up fifth-century Athens, the civilization of which Sophocles was a part, as a pinnacle of human achievement. Even though this was a great time for humanity, Sophocles, a tragedian, was able to hear the note of sadness in the sea, a note which was only to become more strident in Arnold's time. The poet equates the high culture of Sophoclean Athens with that of Christian Europe, which is now also in decline, according to the speaker.