Overall I like the game. The atmosphere and ambience is executed well and when I was around 450m I really just wanted to go back up. The first jumpscare with the lights going out got me as the long waits allowed me to be deep in my thoughts. 

However, I think that the final jumpscare was done too early. I don't think the tension was allowed to build up for it to pay off and when I saw it being a (relatively) normal bug/spider creature it left me more confused than anything as to how it's communicating with me with the Morse code. I'm not sure. Also, how are you attached to the cable? It seemed like I was just floating there. Oh and subtitles at the start would've been nice. I know Iron Lung doesn't have them but I think it should've as well. 

What I think would work great here is to extend the length of the game and develop the story with the Morse code messages more, and perhaps change the monster design so it makes sense given the context of the game (maybe put more artifacts like that weird light thing at the start?).

Anyways, solid little horror experience, was totally immersed throughout.

Really loved this game, and I'm absolutely not a horror game person. Literally when the second message came in and said something along the lines of "come back if danger" I read it as "come back danger" and came all the way back up - I'm so easy to scare lol

Love the premise of this, the slowness / drag just added to the heavy  dark atmostphere, loved the limited ability to communicate, the feeling of being trapped in such a narrow corridor. The scariest part for me was when everything went dark and didnt come back for a good 10 seconds. The sound design is really fantastic, the graphics, while simple, was still very much on point. Everything feels very cohesive and polished. Great job!

Good game, I really liked sound design and atmosphere. The idea is great

Spoilers ahead

When the flashlight went off, I got really scared. I also thought that now I need to feel the buttons in the dark.

And the “screamer” at the end didn’t scare me at all, I didn’t even understand what it was, to be honest.

Spoiler Alert

You might wanna add some scary things along the way. Also, during gameplay i had a few questions. Why don't we react on strange glowing something) and why our mate tell us to go up, but then again down)
But the suspense is great, as well as SFX) The spider got me 😅

Great job!

And also, fix the 'web' artifact))

Spoilers in comment for anyone who hasn't played yet I recommend doing so first!

Great premise! Your sound design was definitely great and the environmental changes had me on edge. There were a couple of scares that I missed I think because the web played didn't load them in time- and I could sort of tell when something was going to happen from the frames lagging but that's not easy to control without a lot of testing of the web build.
I think this is a fantastic idea and a decent first execution but I would love to see it pushed further. You mention being inspired by iron lung, and one of the reasons that game is so effective is because the player is actively having to navigate the world and interpret instructions, learning a new skill to do so.
I think there is a lot of potential untapped horror in giving a player a sheet of Morse code, and letting them replay a message while they decipher it. Perhaps having somewhere they are meant to input the result as well. Iron lung scares you by putting the 'jumpscare' moments in unexpected places so you aren't ready for them. But that is also a much bigger project idea and I think you've done a good job making something effective in the time given. 
Things that were very effective for me were the widening and narrowing of the passage, and being unable to go up. There were several times though when I looked up of my own accord and nothing was there. I think maybe if the tapping got louder and closer sounding people might look of their own volition which would make it a more effective scare. I also think having something move the first time I look down would be good. The web effects looked great, and I loved the eerie light that appeared when it said 'its going to get dark.' the mis-match of information to reality instantly builds tension. Great work!