Elytra may alter hitbox height

With Elytra equipped, Everything mentioned below applies.

While swimming, If a player spam the Jump button to swim up, the same button that activates the Elytra, then at common chance the player's hitbox hight change to 2 blocks tall, not allowing that player to pass through 3 block by 3 block hight hoop in water.

Surfaced or on air, there's a random chance that there wouldn't be a hitbox hight update, in that chance the player hitbox hight be 1 block tall, allowing that player to pass through that same hoop (but on surface) during the player's grounded session. It may suffocate a player in a 1 air block high area unless if the block 1.25 measured above your foot is Glass block, stairs or slabs for example, you won't suffocate. Easiest to test is to be in creative. Build a hoop or 1 air block tall area, then dive down with an Elytra, then quickly unequip it.

The hoop is an example. If you use stairs 2 blocks by 2 blocks to make a hoop, that counts a 1 air block high hoop. You can build anything 1 air block high and you can pass through that build on surface.