[4] Pseudoliparis swirei are abundant in their deep-sea habitat and lay relatively large eggs that are almost 1 cm (0.4 in) in diameter.

[6] Only one other species of fish has been recorded from depths in excess of 8,000 m (26,000 ft), the so-called ethereal snailfish (living in the same region as Pseudoliparis swirei but somewhat deeper), but it has only been seen on film and remain undescribed.

[6] Due to the extreme pressure, 8,000–8,500 m (26,200–27,900 ft) appears to be around the theoretical maximum depth possible for fish.

[9][10] Compared to shallow-water snailfish, Pseudoliparis swirei has several unusual adaptions for its dark and high pressure habitat, including transparent skin that lacks pigment, certain organs and eggs that are enlarged, the muscles are thinner, the ossification of its bones (notably the skull) is incomplete, it appears to have little or no ability to see, there are mechanisms that allow proteins in its body to still function, and differences in the cell membranes for maintaining their flexibility.

[1] There are indications that the larvae of P. swirei and at least some other hadal fish spend time in the open water at relatively shallow depths, less than 1,000 m (3,300 ft).