If the atmosphere’s an ocean, we’re all bottom-dwellers. Ancient peoples populated the sky above with incorporeal beings, starting with a god, or gods, at the top. Beneath that great being were other, for lack of a better term, spiritual beings. Angels, etc. Eventually, the lower you got in the sky, the heavier bodies became until those of us bound to our planet by gravity (for which they had no concept) were pretty much stuck on earth. Although this may not seem like it, it was an early form of scientific thinking. Birds fly. The first thing you notice upon lifting a bird, is how light it is. (Bird lifting may be rare to those of us in modern times, keeping the wonder intact when we actually encounter it. I was once handed an owl-hawk or some such raptor, at a street vendor stand at Stratford-upon-Avon. As the handler slipped the glove on and asked me to hold my hand out, I prepared for like a five-pound bag of flour. Instead I could barely tell that the bird, larger than a bag of flour, was even there. “Light, isn’t he?” the vendor asked.)
Back to science. If birds, which are light, can fly in the air—some at great heights—it must be that sky-dwelling beings are lighter. Lighter than birds. In the Middle Ages, in Europe, this proto-scientific thinking was applied to theology. Monastics and scholastics tried to determine what exactly spiritual bodies were made of. Keep in mind that their world consisted of a basically flat earth with a very large dome over it. That dome had layers—the sun and moon lived in one, the stars lived in one, and then spiritual beings all the way up to God (since monotheism reigned by then). Stories of angels and demons mating with humans circulated. How was that possible if they were pure spirit?
It stands to reason that clouds also inhabit the skies. It doesn’t take much of a scientist to associate heavy clouds with rain. Logic suggests clouds are made of water. Perhaps then spiritual bodies were some kind of vapor. Lighter than air they inhabited realms far above the clouds. They descend by gaining weight, perhaps like clouds. These otherwise ethereal beings would be unknown to us, they dwell so high. They have to come down to deal with us. There may be realms even lower, but if the atmosphere’s an ocean, early science suggests, we are indeed bottom dwellers.