Crawler

Crawlers are an extraterrestrial species of aquatic creature that mostly resemble crawfish and shrimps on Earth. They're considered the most common known species found within Europa's oceans.

Biology
Crawlers are arthropod-like in terms of anatomy, and while individuals are as long as a Human is tall, they're considered one of the smaller species to be found on Europa. They possess three sets of eyes and three legs, accompanied by a set of pincers. Their bodies are covered in a highly-resilient carapace for protection against larger predators, with their head and underbelly exposing their red fleshy skin.

Behavior
Crawlers are hardly ever found alone, and like krill or shrimp on Earth, are often found in large groups. Some smaller groups, or hunting parties, can have at least two to three individual crawlers. This isn't entirely pack behavior, though, more to compensate for their "small" size.

Explorers of Europa often describe shoals of crawlers within the oceans, attacking their vessels and doing combined damage to both crew and their submarines. They have also been reported to have a taste for Human flesh, though more likely, these are scavengers, and more likely to feed on the corpse of a Human rather than go after a live one.