

Spacecraft tend to behave like actual ships floating in water, almost always navigating along the horizontal plane and rarely seen in any other orientation other than "upright", unless they are "sunk". Some works of fiction blur the line between spaceships and oceangoing vessels even further.Though works on the softer side of Mohs Scale of Science Fiction Hardness can justify it with advanced technnologies. Spacecraft even have "lifeboats" - generally called escape pods or something similar - despite the concept being largely impractical in case of realistic space travel.

Good luck finding a Space Schooner or Space Canoe - though they have shown up.

Maybe it's the romance, maybe it's the adventure, maybe it's the obvious parallels to the Age of Exploration, but for some reason, when people write about space, they tend to make parallels to the sea, as President Kennedy (himself a former naval officer) did in his "Space is the new ocean" speech.
