Same.

I also have megalophobia specifically related to ducting and that picture set of my panic response. I hadn’t really thought too much of it, but I wonder if Thr Empire Strikes Back is to blame.

likewise, learning to sail as a kid and having to go around these large partially submerged objects just kicked off some irrational fear in me (and stil does today, though to a lesser degree).

I agree with you, that would be the exact word I would've used to describe it. Also, since I was a child, I've been scared of pool drains for the treatment system.

I have a theory that this, like fear of heights, claustrophobia, agoraphobia etc. are actually "extremely natural" because they're all good for survival ie. instincts unlearned somehow culturally, but would be the baseline if you teleported a Palaeolithic, Sumerian, Viking or whatever into our modern complex and somewhat claustrophobic technological life.