Crouching inside of slab not crawling/swimming

So I was just in 1.14 Pre-Release 2 testing about with the new crouching when I pushed a slab onto my head and my character didn't start doing the swimming animation and instead just stayed crouched. I don't exactly know why this happened. If you need any more info, I can give it to you.

in the 'Environment' section, idk if u need those things but I am running java edition. if you need more on that, I can give that to you too