I think i found a new bug since i can't find it on this forum.

Video

I have found it is possible to swim in the air near the roof of a building. It is underdetermined of the blocks on top, i don't know what to say. If you try and go out of the tunnel, you float a little (around a slab) then drop back down taking no fall damage.

When looking at it from another angle, it is obvious that the person doing the glitch is swimming.

The person hosting the server is on a PS4 on hotfix 1.16.40 and I am on Windows 10 and another player is on Xbox and all can do it.