a friend lent me a number of paperbacks of the "Dumarest" books by E. C. Tubb; I just finished the first first one and found it a surprisingly meaty read, so I am onto the second. and here we are presented with the notion of a lighter-than-air creature that buoys itself up with hydrogen gas. that seems, superficially, a plausible idea; certain Earth bacteria generate molecular hydrogen so an organism that uses H₂ for keeping itself aloft doesn't seem out of the question.
~Chara