abyssopelagic

ah-BISS-oh-peh-LAJ-ik

Of or relating to the ocean zone between roughly 13,000 and 20,000 feet deep — the abyssal waters above the seafloor. Below the bathypelagic zone and above the hadal zone (the trenches). Perpetual darkness, near-freezing temperatures, and pressures that would implode a submarine. Life here is sparse, slow, and strange.

Etymology

Greek abyssos (without bottom) + pelagos (open sea). The bottomless open sea.

Notes

The deepest point in the ocean is the Challenger Deep, located in the Mariana Trench in the western Pacific Ocean at 35,876 feet below sea level. It's named after the HMS Challenger II, which first surveyed it in 1951 (1951!). Only a handful of people have ever reached the bottom — Jacques Piccard and Don Walsh made the first crewed descent in 1960 in the bathyscaphe Trieste (in 1960!), and James Cameron made a solo dive in 2012.