A zone of the ocean between the sublittoral and abyssal, the continental slope, within a depth of 200 lo 3000 m. Its population is poor, existing at the expense of organic matter from the surface layers. Among invertebrates, there are many brachiopods, ten-legged crustaceans, mollusks, echinoderms, and others. Among fish, longtails and charcoal fish are common.

Conditions:

High pressure (up to 25 MN/m² or 250 kgf/cm²).

Almost total absence of light.

Small seasonal temperature variations.

Little seasonal variation in water density.

Water mobility - relatively weak, but much greater than in abyssals.

Bottom topography - dissected.

Seabed sediments are patchy and there are numerous bedrock outcrops.

There is a remarkable diversity in fauna, and in the lower bathyal there are many fish species, which are transitional to abyssal forms.

Vegetation is very poor due to lack of light.