This bug only happens in first person, and at certain angles. I'm not sure if it happens at specific times, but it's guaranteed to happen most of the day.

NOTE: I'm using the latest version of the "green CODE button", because I like to use Bliss Shaders together with Distant Horizons.

attachments:

what on earth...
to isolate the problem, could you please test if this happens with only the mods: iris, sodium, indium, and distant horizons?
this will determine if its a conflict from one of your other mods.

only Iris, Sodium, Indium and DH💀:
*edit: then I even deactivated my Resource Packs and it continued like that

these 2 things im about to say are unlikely, since it changes based on camera type lol, but im grasping at straws now

the shader can read a resourcepacks textures that it might make for shaders that controls reflections, so removing all resourcepacks to check is a good idea

have you changed any shader settings at all? there is a reset button for it within the shader settings
located in video settings -> shaders -> shader settings

I will link this here: https://gitlab.com/distant-horizons-team/distant-horizons/-/issues/861#note_2203695281
Read the linked comment and the next after that to get some potential fixes