I loved reading this, I hadn't had the time to leave a comment previously but I'd certainly like to leave a couple of thoughts!
The fear of the ocean depths, of what could be lurking down there, or how many wrecks dust the seabed where human eyes will never see again, it was these thoughts that, weirdly enough, inspired me to get in to SCUBA diving! I always wanted to be a wreck diver and, on a couple of occasions going to down to one, seeing the shape slowly come out of the gloom by flashlight is absolutely thrilling. I don't have the same fears as yourself but I feel we have similar levels of fascination with this vast, dark, alien world.
Also wanted to quickly mention the sound design. I'm fortunate enough to have a surround sound subwoofer aided system set up in a relatively small space. Stepping in to the deadzones and hearing the bumps and the low background noise, was really quite a thrill aha. Just one of those things that you can appreciate with good sound design as I started feeling more and more spooked (playing in pitch black also helps a lot!).