What makes stories of the sea different from stories taking place in other settings? Wikipedia has a nice, short entry touching on this question and I agree with its authors about the themes common to such stories and I won’t rehash those here. By their very nature, sea stories create interest because the setting is different from most readers’ land-dominated lives. People who have never been to sea are curious about what life is like out there. Those who have been to sea enjoy relating to the experiences of the story’s characters.
The ocean makes for a paradoxical setting in that it is always in motion, but never really changing. For the most part, the land just sits there, but the surface of the sea moves in a restless, rippling, chaos of crests and troughs. The characters look out from their vessel and see a continuous display of nature’s power. In general, this cannot be said about stories set on land or in outer space. However, despite all this motion, water has a dull sameness to it. Other than varieties of waves and some differences in water color, there’s little to distinguish one patch of ocean from another. The sea shares this characteristic with outer space. However, land provides a much wider variation in appearance, giving a descriptive writer more paints and textures for his word palette. I think that’s why sea stories tend to skip over descriptions of the traveling part, compared to stories set on land.
I regard the ocean as a setting more illustrative of man’s creative powers. We can stand up and move about on dry ground without any special assistance at all; we possessed from birth everything necessary to do that. But the only way we can survive for long at sea, or travel through it, is through an act of creation—we must first build a vessel. So stories based at sea must intrinsically involve a demonstration of our tool making skills and our exploratory urges. The ship itself shows man’s genius and his desire to conquer nature, to test its limits.
I said I wouldn’t rehash the Wikipedia article, but I can’t resist emphasizing what it states its description—how stories set at sea possess a crucible aspect. The characters have limited contact with the rest of humanity and must deal with each other in a confined vessel from which there is no easy exit. They must confront their problems using their own personal attributes and whatever materials they have on hand, without the assistance of outsiders. The reader can easily see their plight and focus on it.