The optional points of interests

The game being popular, I thought there'd be a guide for this by now. That fandom site is really annoying without an ad-blocker.

Additional notes:
- Going straight to any of these areas without taking all or any photos will still trigger all the scripted events (steam leak, fire, etcetera, even the oxygen depletion which can't actually kill you).
- Look up those out-of-bounds videos for clearer footage of these things and more general info.

(Brick walls) X_375, Y_567, A_just face the wall

In case you missed it the first time like I did.
As you're making your way toward the upper part of the map, just be in the general tight-path area where it's blurred on the map. When your sub detects that you're in between walls, just face your sub directly toward them to look at bricks and pillars. Wow, ancient bricks.

(The eye) X_456, upper half of map

No specific coordinates because it's scripted to happen when you're on the upper half of the map and you hit a specific vertical line around the X_456 area.
I included this in the guide because me and some other people apparently somehow missed it the first time, even though it seems like you're not supposed to miss it.

Map image taken from a video by "sapphireHESUS".

(The top right node) X_675, Y_828, A_295

AKA: The "You've Played this Before" achievement.
It's marked on your map. Just go there without it being the last photo you take so the game doesn't end.
The interest itself is just the same exact one as the required X_864, Y_258, A_209.

(secret) X_780, Y_706, A_161

(secret) X_870, Y_845, A_44

It's especially special because it makes a spooky sound, too.