On a default superflat world, some chunks appear to be 'invisible', despite the F3 menu displaying a grass block being present.

When flying over this chunk in Creative Mode and then landing, the player appears to slowly float downwards. Once landed, the player move up and down quickly, but cannot move horizontally, nor can they jump, however they are able to fly back up.

The player is also invisible is F5 / third person.

Occasionally particles of blocks being broken also appear.