Echoing Horror

Shallow sea is a rather uneventful place. The shallow water with rocks underneath doesn't hide anything interesting.
But, once in a while sailors stumble upon what is called an Abyss pit which, as the name implies, are so deep, sunlight doesn't reach the bottom. While there are no signs of life, sailors report echoing howls coming from their depths, as they sail by. What makes these sounds was unknown for a long time, but it was and still is enough for locals to avoid them.

Description:

Echoing horror is more of a creature than a fish. About 2 meter long slender bodies with dark slimy skin, around 12 rather short tentacle-like apendages it uses to hold onto the pit walls. 6 empty white eyes are set on top, observing any signs of potential food.
The Creature seems to be only able to crawl, as it has no fins.

Biology and behavior:

Much is unknown about it's biology and behavior, but what is, makes it out to be a true horror from the depths. It has a mouth with thin jagged teeth that is able to shoot out half a meter outward, trapping it's prey and dragging it back.
In terms of sight it appears to be able to make out thing up to a meter in complete darkness. It's breathing is rather strange however. It breathes in once every few minutes, thanks to it's slowed metabolism, due to a low food availability. When it does so, thanks to the nature of it's habitat and breathing, an echoing howl comes to the surface, terrifying local sailors.
It appears to be an omnivore, feeding literraly on anything that it can.