I think that filling the entire spaceship with perfluorocarbon liquid is an interesting possibility for long duration spaceflight. The oxygen solubility would allow breathing. The high electrical resistivity would allow electronics to work with great heat dissipation. Fires would be self extinguishing. Leaks would just be dribbles. The high density (near 2 g/cc) would cause much more physical exertion to maintain physical strength, simulating at least a little bit of gravity. Could this stave off bone loss? I doubt if I am the first one to have this idea, perhaps there is some critical flaw (it's damn heavy, 4 1) ? But this seems like a very interesting possibility to me, an alternative fluid media for human living. Has anyone ever