Bigbadcuff

You are running Minecraft on the Playstation 5. The PS5 doesn't have java edition Minecraft and only has the other version of Minecraft called Bedrock edition. This report would be labeled a false report

Not enough information (seed, F3 menu opened, and how to reproduced are needed to have a well made bug report.) 

I think you are correct (Tail) in saying that this report is a duplicate of MC-1448. 

This isn't a bug as far as I can comprehend your bug report as the elytra changes were only in the experimental snapshots for 1.18. The elytra is still using its original system of reducing durability. `    

Mojang in previous snapshots for 1.18 had made dungeons more common under y-level 0. I would not call this a bug based on the evidence you have provided (not saying its useless). Take this with a grain of salt, but I think this isn't a bug and it will be just perhaps listed as "Working as Intended."     

Related/duplicate of MC-236676 

I can confirm that this does occur in 1.18 Pre-release 1. I have posted some more screenshots of this bug on this bug report. All my added screenshots are from the same seed, 2896381056570021028. This can be recreated by typing in this seed and teleporting to the coordinates or create a new seed and find a frozen ocean. 

I will try to reproduce the issue without optifine and see if the issue is still present.

Thank you for the feedback!

 (Update) Discovered that the bug was not present with any mods added to the game, and please ignore this bug report. Thank you to the people who commented to make me aware of this.