Before the bug occurred, I had been AFK in water to let kelp grow. I was climbing out of water and two Phantoms spawned, so I equipped my Elytra to get away from them, however, after activating flight, everything stopped moving, the Entity Idle animations like the flapping wings on the Phantoms persisted, but the phantoms themselves stopped moving and making noise. This became true for all other entities, hostile mobs would not aggro and animals didn't move. Additionally, after removing the Elytra, I was still in flight state and could not land or take damage, if I was touching the ground I could jump the normal height. I was still able to interact with blocks to a degree; doors still opened, buttons and levers became stuck in the activated position without redstone outputs. mine carts still moved, and nether portals still had their effects but could not transport anything.

Attempting to quit from the world resulted in the game freezing on the saving world screen. the X button and alt+F4 did not work and the game had to be closed using task manager, at whcih point the launcher opened and gave me the "Minecraft has crashed due to an unexpected error" message. After re-opening the game, I was back at the water before the Phantoms spawned and everything began to run normally again. I have not been able to recreate this bug. Attached is a screen recording of things that happened during the glitch from a friends POV.