• A hostile leviathan that doesn't care to make themselves unknown.

• Can be found swimming outside of Bay Reef perimeters.

• Many of these get hunted for resources.

• Their antenna are filled with a liquid that has been used to preserve or rapidly heal wounds.

(https://www.reddit.com/r/subnautica/comments/ydu13b/no_spoilers_fan_leviathan_by_rebecca_el_cheikh/ 

• Massive passive creature that patrol near shallow waters.

• Enderians feed these leviathans and in return they keep the terratories near them protected.

• They use a form of echolocation, in doing so creatures within a few miles are able to hear its deep bellows.

(https://www.reddit.com/r/subnautica/comments/1l2ppch/our_creative_community_couldnt_do_without_fan/ 

• Large manta ray like beings, they remain in spaces that are deep and dark.

• Often found more in void spaces.

• Silent in movement and will stalk any unsespecting creature that enters their vacinity.

• Surges of energy causes them to let off a glow.
  
  
  (https://subnautica.fandom.com/f/p/4400000000000094248/r/4400000000000286160 

• Large ancestors to small docile axolotls.

• Neutral unless provoked, hard to escape once being hunted.

• They use their claws or jaws to attack prey.

• The fins along its body secrete an acid like substance, making them harmful to touch.

(https://www.artstation.com/artwork/zxqn4Q