I found this glitch where you are able to clip through blocks and be able to crawl under 1 block spaces, and even have the crawling animation using this same glitch on a half block.
Video: (ps i kinda got lucky on the first attempt lol)
I don't have any hacks installed, just some forge mods to help with lag (as you can see im very laggy anyway lol). Please check this out as this can be used to cheat through games and other stuff. (1.15.2)
EDIT: PART 2 https://streamable.com/7z35yj
Don't really understand, because it seems I am clipping thru the blocks. Like the wall is moving me to the side and into the crawling position.