Most specimens of O. depressa live in the ocean's bathyal zone, where sunlight doesn't reach.

[4] The first specimen described by scientists was found about 16 km (9.9 mi) west of Cape Sunosaki in Japan.

Like other members of the cirrate octopus subgroup, it has a fleshy web connecting its arms, a small internal shell to support its body, fins to help it swim, and small fleshy tendrils called "cirri" lining its arms.

[7] O. depressa hosts the parasite Dicyemennea umbraculum,[2] which belongs to the larger group Dicyemida.

In the early 2000s, scientists studied the mitochondrial DNA of some coleoid cephalopods (octopuses, squids, and cuttlefish).