The way I look at it which is kinda overly simple is you are creating a ripple in the medium you are pushing or pulling and that ripple is moving at the speed of sound for whatever the medium is made of.

Big enough objects over large enough space/time act much like liquids do, both with movement acting like a fast moving ripple and the natural slow movement/flow( takes thousands to many millions of years slow) on its own driven by its own gravity I believe like the Earth's deep layers.

If we had the tech in theory could we not say bypass breathing with a device that oxygenates blood then fill all air gaps with a liquid/gel that's made for it's density and to be non harmful instead of focusing on breathability.

After that maybe a flight suit to contain/ keep separate the different liquids/gels. As well as maybe a liquid only feeding tube as well as what ever you will need to capture the "waste" after lol. Things needed for extended use.

I like to invent hypothetical things and try to find ways to make them real and this is a fun one, out of my wheel house to attempt though even if I still had my workshop sadly. Oh how I miss trying to build a food generator for real.