In the poem "The Seafarer," what does the speaker endure on the sea?

"The Seafarer" is an Anglo-Saxon poem which is narrated by a seafaring man who tries to explain why why he loves the sea despite the horrible hardships he has to endure there.

The opening lines of the poem make it clear that life at sea is a miserable thing. He experiences "sorrow and fear and pain" on every ship and in every port (which is many), and he has experienced the "smashing surf" as he

sweated in the cold

Of an anxious watch, perched in the bow

As it dashed under cliffs.

As he keeps watch, his

feet were cast

In icy bands, bound with frost,

With frozen chains, and hardship groaned

Around my heart.

As difficult as the physical aspects of living on the sea are for him, it is the soul-deep hardships which are the worst. His "sea-weary soul" complains that no one who spends their days on land can understand "how wretched" he is

drifting through winter

On an ice-cold sea, whirled in sorrow,

Alone in a world blown clear of love,

Hung with icicles.

The seafarer experiences hailstorms, seas that roar, and "freezing waves." Instead of the comforting sounds of laughter, love, and nature which people on land regularly experience, the seafarer only hears 

the cry of the sea-fowl,

The death-noise of birds instead of laughter,

The mewing of gulls instead of mead.

Storms beat on the rocky cliffs and were echoed

By icy-feathered terns and the eagle's screams.

At sea, there is no comfort from family and friends, and his soul is often "left drowning in desolation." All of this is a stark comparison to living on land, in cities filled with passions and pleasures and no trouble. This is, of course, an idealized view of life on land, but it is certainly a sharp contrast to his life on the sea. 

When the seafarer has to leave land and go back to the sea, he is not happy; in fact, he is most miserable. Before long, however, he once again feels the waves rolling beneath him and is greeted by the sea-birds.