What is the theme of "The Boatman" by Vasily A. Zhukovsky

You could find several themes at work in this poem, but in my opinion, the central one is about having faith in a higher power even when all seems lost and there's "no hope for salvation," as this poem's speaker worries in the second stanza. Lost at sea, caught in a storm, and surrounded by cliffs that will surely sink his boat and lead him to a watery grave, the speaker has an understandably "heavy spirit." However, in the very next line he calls himself a "madman" for forgetting that "Providence / was [his] secret helmsman." Once he remembers that he is under the protective care of God, the "hand invisible" of the "all-powerful savior" guides the boat away from its precarious position and into a "paradisical realm" where three celestial angels await him.
Rendered speechless at the "holy innocence" and "aura divine" that these angels radiate, the speaker decides to "live and breathe for them; take into my soul and heart / all their words." Having wavered in his faith while lost at sea, the speaker here recommits to a life of faith in which he will try to live as purely and goodly as the angels do. Out of a near-death experience, this poem's speaker finds a strengthening of his belief in a spiritual power. Thus, I would argue that Zhukosvky's poem encourages us to consider the ways that God's protection is unwavering and can always teach us something, even when we are in the throes of despair.