Flight And Freedom.
In American sf, the supreme symbol of freedom is flight between the stars although, paradoxically, while travelling, interstellar astronauts are usually confined within a metal hull, as Poul Anderson sometimes pointed out. Some fictional characters address this problem. James Blish's Okies fly cities. Anderson's asterites move a hollowed out asteroid with an internal environment and ecology. Dominic Flandry's interstellar speedster is sybaritic.
To make another comparison between space and the sea, James Bond, surveying the interior of a very expensive yacht, comments that the right way to treat the sea is as if it did not exist.