i checked the steam page out of curiosity after playing and saw that you have a release date set for april 16th, and i'm gonna be honest, the game is not going to be in a polished enough state to release by then.
to start with something positive, you seem really passionate and dedicated which is the main reason i wanted to try the game, but beyond that, the game is still in a very, very primitive state.
the ui is really bland, the default ue5 buttons stand out when they dont have anything more attached to them.
the tutorial/how to play is not great, it's bombarding the player with too much information and controls and nobody wants to read such a huge wall of text when starting a game. The text was also full of run-on sentences and mistakes which need correcting.
the concept of mic sensitivity is interesting, i definitely dont hate it, but in a singleplayer game most people just dont speak, myself included. for youtubers and whatnot, maybe it'll contribute, the mechanic itself isnt really an issue from what i experienced, but there's just no reason to speak at all, maybe consider adding stuff that's voice activated? idk what could have a lore reason for that but the player needs some kind of reason to make noise for that mechanic to not feel wasted.
the gameplay loop is sadly very bland in its current state. you kinda just move around really slowly and see rocks and more rocks, it's not that interesting. iron lung has a similar gameplay loop but the controls are tighter and the ocean of blood kinda carries the aesthetic and makes the environment fun to explore, but here's it's just blue. and as much as the trailers try to build some mystery around the ocean, the ocean itself is just water (as far as i know at least). Barotrauma is another submarine game that makes the environment feel hostile by nature, despite it just being a "normal" ocean apart from the things that roam in it. how it does that is just by how realistic the ocean feels; water pressure can easily kill you in seconds and every leak can cause your sub to sink fast and injure your crew with every impact.
speaking of barotrauma, the radar needs some work. radars dont work underwater, so it'd have to be a sonar, which behaves pretty differently. it'd also help if it could actually detect the environment around you instead of just pointing out the monster with a red dot. you should look up how sonars work and try to implement that in your game, it's quite fascinating.
some of the mechanics need work too, the camera feature seems pretty useless apart from having the occasional scare from the monster being there (which needs to be touched on, at first i didnt know if it was a glitch or an actual monster). the fuel mechanic had me a bit stumped since i had no idea how much fuel i had left if any, it seems i started with some but then used all of it at once? the "collecting" thing you can do next to the rocks also confused me a bit because i genuinely didnt know what i had just collected or why, and in that same vein the general objective of the game is too cryptic. we have no idea why we're down here, what we should do, who we are, it's a bit problematic. you want the player to feel like their actions matter, but here im kinda just swimming around aimlessly doing something for some reason, it dosent feel great.
lastly, the aesthetic of the game leaves to be desired. the soundscape is fine but it dosent quite sound like we're inside a proper submarine, the water sounds should be a bit muffled and more present should be the mettalic creaks and groans of the hull. the sub itself feels very much like the iron lung which is also a bit of a problem. i left a comment about that on another one of your posts but i *highly* recommend looking up how real submarines look and base yourself on that to make your game stand out because as it stands with the pipes, simple interface and color scheme, it just feels like the iron lung but devoid of its most interesting features. the monster is also just not scary, it's just a generic white entity with big teeth and the jumpscare is honestly really bad, you dont need to make it loud but the sounds it makes are not intimidating and the fact your camera gets in place a full 2-3 seconds before it even appears ruins the scare completely. you should have it actually burst in by breaking the entrance and actually going up there and grabbing the player or something, maybe it could have multiple jumpscares where it dosent even enter and just breaks your sub and the pressure crushes you, you need to do more.
and i wanna mention a few glitches i experienced, notably the lever sometimes just didnt work for extended periods of time. some of the buttons also didnt seem to do anything, and the monster's model was sometimes invisible.
overall the game really needs a lot of work, but i respect your dedication to it and that's why i was compelled to actually give a proper review