How does the theme of "the tide rises, the tide falls" develop as the poem moves forward?

The poem Tide Rises, The Tide Falls moves while providing the readers the information that there is life after every end while using nature as the key element of the poem. Nature has been described as gentle but violent. Realizations of death have also been present in this piece. The writer shows that even death is inevitable and part of life, life moves on after it. 

The poem’s overall theme changes from one that shows the wonders of nature to one that manifests a fright of it. What is developed in the poem is the natural imagery which depicts that nature will keep on going even after humans will cease to exist.