Darkness

"The Tides Rises, the Tide Falls" is a very dark poem, figuratively and literally. The bulk of the action takes place at twilight, a fact the speaker keeps reiterating. In the first stanza we are told that the twilight is darkening, in the second that darkness is "settling" on the "roofs and walls" of the town and that, somewhere out there in that darkness, the ocean is calling to somebody or something. More than anything else, darkness is the poem's primary symbol of death, of the transition from mortal life on earth to something else. While the sun rises in the poem's final stanza, the literal darkness of the first two stanzas is still present in the fact that the traveler has died.

• Line 2: The darkening twilight here symbolizes death and implies that "The Tide Rises, the Tide Falls" will be a poem about, well, death and dying.
• Line 6: The darkness of night settles on the town, and again the darkness symbolizes the inevitability of death. 
• Line 7: The eeriness of line 6 is amped up here as the voice of the ocean cries out somewhere in the darkness. We get the sense that the personified ocean is calling for the traveler's life, or something creepy like that.