Hi !

I noticed that when you fly in Elytra and launch a firework in a minecart (to sit in) without the rail and with a slab into it, you will be teleported into the ground and you will see trough the blocks.

When you shift for leave the minecart, you will be teleported back above the minecraft.

I've replicated it multiple times.

I hope this will be helpful,

Linkle96