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 "ballast sac". On the front, three elongated dark brown tentacles protrude off the shell. Underneath the ballast sac, the "skirt" is made of thinner black tendrils.

Molochs are blind, and rely on using echolocation to navigate the ocean. The ballast sac, 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 and projectiles.

The Moloch can either 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 and loud devices. 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 especially defensive when rearing their pupae.

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.