In the opening line and on through the first twenty, the speaker of this poem is miserable. He describes his experience at sea as being in constant "sorrow and fear and pain" (line 3), "suffering in a hundred ships,/In a thousand ports, and in me" (lines 4/5). He is "hungry" and "wretched" (lines 12-15).
Not much gives the speaker comfort. In lines 19-22, he says sarcastically, " The song of the swan/Might serve for pleasure, the cry of the sea-fowl,/The death-noise of birds instead of laughter,/The mewing of gulls instead of mead." He obviously would rather be somewhere warm with a cold beer!
But, even though the challenges are enormous, the discomfort real, the fear palatable, the speaker feels drawn to the sea time and again. Challenging the elements, he feels closer to God himself and more appreciative of life. In short, adversity makes him feel alive: And yet my heart wanders away,/My soul roams with the sea, the whales'/Home, wandering to the widest corners of the world, returning ravenous with desire/ Flying solitary, screaming, exciting me/To the open ocean, breaking oaths/On the curve of a wave./Thus the joys of God. (lines 60-65)