I think this is a myth that gets propogated online without any citations. Giger's "Necronom IV" painting from 1976[0] was the inspiration of the xenomorph in "Alien". Is there any evidence this painting was in turn inspired by deep undersea creatures?

[0] https://upload.wikimedia.org/wikipedia/en/d/db/H.R._Giger_-_...

I believe the article I linked mentioned the thought being that it was the queen from Aliens, not the original xenomorph. I also wouldn't be surprised to find it to be untrue altogether, thus the "believed to be" phrasing.