Nether portal under y 0 teleports to the void

After creating a nether portal under y 0 in the overworld, specifically in the center of an ancient city, i got teleported under what seems to be the nether floor at around -600. Though i should be in the void my character isn't receiving any damage or anything. The y level is getting lower and lower at lightning fast rates, and it doesn't seem to stop (in a few minutes at level -27 000) . My player body is in a crouched position, stuck in a walking animation and is very glitchy in the inventory. Everytime i rejoin the world it teleports me back to approximately y -600, probably corresponding to the y<0 level in the overworld.