The concept of a "sky ocean" with various air born organisms making up the base of the food chain is one of the most interesting ones made up by the creators of these programs, it gives the worlds a different feel to them and makes for interesting food chain arrangements. Darwin 4 is a very nice example of this, and makes an interesting projection of what the ecology on a planet would look like should there be no oceans. The idea of massive "sky whales" and giant floating creatures that feed upon these small "air plankton" is a particularly interesting product of such an ecosystem, imagine if the existence of these microflyers and airborne plants could give rise to more than single bodied organisms, imagine a swarm of highly specialized, insect like creatures that inhabit some sort of giant floating ant hill constructed through the shedding of organic tissue by specialized individuals of the "hive" and made to float through the harvesting of the hydrogen/methane from within the bodies of other large floaters. Life can take on many challenges and thrive, though we cannot yet see such alien life, the creative minds of the many authors and producers mentioned on this thread are doing a wonderful job in giving us incites into how different some of that life may actually be.
