What hardships of the sea does the narrator relate in The Seafarer?
The narrator relates the fear he experiences, being at the mercy of the elements, in lines 6-8, "Of smashing surf...Of an anxious watch, perched in the bow as it dashed under cliffs". He mentions hunger (line 11), and makes several references to inclement weather, especially the cold - "My feet were cast in icy bands, bound with frost" (lines 8-9), "How wretched I was, drifting through winter on an ice-cold sea" (lines 14-15), "icicles...hailstones...freezing waves" (lines 17-19). He also talks about isolation and loneliness of life on the sea in lines 25-26, "No kinsman could offer comfort there, to a soul left drowning in desolation".
I love this poem! The Seafarer does indeed relay all the hardships in your former answer, but he also relates how he is heartsick when he is not at sea. It is a longing within his breast that he can never escape. When he is at sea, he is happiest--in spite of the cold, the harsh weather, the premature aging of his body due to the harsh conditions. When he is on land when he should be happy with the comforts of home, drink, food, the company of women and family, all he wants is to be back on the sea. This is an enormous internal conflict, as the narrator undoubtedly will not be able to live the life of a sailor forever.