Elegies can be laments for the dead. They can also be self-reflective poems. This is the case of "The Seafarer." Elegies are most notably mournful and melancholy. Although elegies were initially defined by their structure and general tone, they came to be known primarily for their subject matter. And the themes have something to do with sad reflection, laments for the dead, and a mourning of some kind.
"The Seafarer" gets right into a self-reflective mourning:
This tale is true, and mine. It tells
How the sea took me, swept me back
And forth in sorrow and fear and pain
Showed me suffering in a hundred ships,
In a thousand ports and in me.
The speaker is mourning his very existence as though it were a death in life. He uses words associated with profound sadness and coldness to describe his predicament: "an ice-cold sea, whirled in sorrow," and "a soul left drowning in desolation." He mourns his life and because of the dangerous nature of his occupation, he fears his death. The speaker also notes how fleeting life is with "life itself / Fades quickly into the earth." So, even though he feels desolate in his own life, he still laments the fact that life is so fleeting. The speaker's only solace is the promise of Heaven. He continues speaking of graves, lost kinsmen, and memories of those departed. All of these are themes typical of the elegy.