Moloch (Barotrauma)

The Moloch is a very large, ponderous, jellyfish-like creature found within Europa's vast oceans.

Biology
Molochs bear a resemblance to an extinct Earth creature known as Dollocaris. The Moloch's large dark blue shell covers most of its main body, which seems to be mostly made of the creature's brain. On the front, three elongated dark brown tentacles protrude off the shell. Underneath the brain, the "skirt" is made of thinner black tendrils.

Molochs are blind, and rely on using the sensory tendrils which line the ventral side of its body to navigate the ocean. The brain, or core body, can pulsate to provide propulsion. They emit strikingly tuneful notes, stronger and higher in tone when the creature attacks.

The Moloch's shell serves as both defensive and offensive capabilities. It protects their soft innards from predators or falling debris.

The Moloch can also ram into its targets, or whip them with its tentacles.

Behavior
Interestingly, these creatures are dangerous to expeditions, but not directly towards divers as they tend to focus their attacks on approaching vessels. This is possibly due to misidentification for another Moloch or a larger predator, and they could be doing this as a defensive tactic to drive the threat away.

Molochs are very vocal creatures, and are capable of emitting a surprisingly varied amount of tuneful notes, which vaguely resemble the calls of Earth whales. These calls have even been known to reach infrasound levels, and some expeditions have mistaken their presence for alien artifacts within alien ruins.