He is drawn to the sea. It is in his blood. Have you ever loved anything so much that you're constantly thinking of it and want to get back to it? It's like Lance Armstrong with biking, or Michael Jordan with basketball.
The speaker of this poem is in love with life on the sea. No matter how cold and uncomfortable it is, or how hard the work tends to be, he can't keep himself from this life. He recognizes that life on land is easier and more comfortable and that there is no shortage of warm beds, food, and women on land. However, that is not what entices him. The sea calls to him and beckons him back.
In "The Seafarer," the speaker is constantly drawn to the sea. He talks about how his "soul roams with the sea", for instance, and how he returns to the sea "ravenous with desire." In addition, he notes his excitement in being out on the "open ocean."
It seems odd that the speaker is drawn to the sea, considering that early in the poem, he describes it as a wild and unpredictable place where "icy bands" and great "hardship" lie ahead. This, however, leads to his central message: that the sea is a place where "worldly pleasures" do not exist nor matter. The sea does not care about one's pleasure for women, for example, or about pride and greed. In fact, this is exactly why the speaker loves the sea so much. It provides him with an opportunity to be at one with nature and, in turn, closer to God. At sea, he conquers his pride, rallies his strength and realizes that life is not about material comforts or concerns. Instead, the need to survive out of sea reminds the speaker that God is in control of the world and that it is God who truly matters.