So this is a cusk eel in the genus Bassogigas.
The elongate body that a lot of these fish have is useful in this deep-sea environment for several different reasons.
It gives them an eel-like swimming motion that uses relatively little energy compared to the standard way
fish swim by wagging the tail and moving fast, because energy is at a premium in the deep-sea environment.
It also increases the length of the lateral line, the line of vibration-sensing organs along the body.
By tilting the body slightly, the eel-like swimming tends to drive the body down and enable the fish to stay closer to the bottom.
Now you can see, or I can see on my lag, that this fish has elongate fin rays on the bottom, just behind the head, those have a sensory function, too.