If you swam into a one-block place and died in this place, after respawning, your hitbox will not update, that means your hitbox is still one block high and you can go through one-block holes.

Steps to reproduce:

1.create a one-block hole and fill it with water.

2.swim into the one-block hole and kill yourself.

3.click the "Respawn" button and respawn.

Observed results:

Player can go through the one-block hole.

Expected results:

Player cannot go through one-block holes because player's hitbox is higher than the hole.