Attitude: Passive
Edible
Food Value: +16
Energy Value: +210
The Bladderfish is a small, passive fauna species. It is mostly found in the Safe Shallows and the Grand Reef. The Bladderfish stands out in comparison to other small fish, as it can be used to craft Filtered Water. As a result, Bladderfish are a good source of H2O, though not as good as Disinfected Water and Large Filtered Water. Eating a raw Bladderfish will restore fifteen points of Oxygen, which can save the player in certain situations. Additionally, a Bladderfish is required to create the airbladder tool.

Attitude: Passive
Edible
Food Value: +21
Energy Value: +280
The Boomerang is a small passive fauna species. It is extremely common and found in many biomes. The Boomerang sways side-to-side as it swims. If approached by the player, it will eventually flee. It is a fast swimmer, and is usually found to be very active during the day. During the night, it usually finds shelter near the caves or the seabed. They are commonly seen in Shoals around the map.

Attitude: Passive
Edible
Food Value: +18
Energy Value: +420
The Eyeye is a small, passive, herbivorous fauna species. It can be caught and is edible. It possesses moderate food properties, and does not reduce hydration when consumed, making it a decent food source when a player is unable to cook any food. Eyeyes are very common and appear in many biomes, also spawning in large numbers in the Jellyshroom Cave.

Attitude: Passive
Edible
Food Value: +18
Energy Value: +420
The Garryfish is a small, passive Fauna species, usually found in the Safe Shallows and around the Underwater Islands. Although Garryfish only yield average Food points when cooked, they move fairly slow, making them easy to catch. The Garryfish is a type of solitary prey and is mostly seen gliding slowly and aimlessly within its vicinity. It ignores the player completely.

Attitude: Passive
Edible
Food Value: +21
Energy Value: +280
The Holefish is a small, passive fauna species, usually found near and within small caves. It is catchable and edible. The Holefish is very agile and evasive, often seen darting around cave systems' entrances alone or in shoals. It flees when approached by the player.

Attitude: Passive
Edible
Food Value: +23
Energy Value: +280
The Hoopfish is a common, passive fauna species that can be found in many Biomes. The Hoopfish is fairly easy to catch, as it doesn't retreat upon being approached by the player and is easily recognized due to its bright bioluminescent glows. The Hoopfish is a rather slow swimmer, and is mostly seen forming shoals in various biomes. It would often try to flee if approached by the player.

Attitude: Passive
Edible
Food Value: +32
Energy Value: +420
The Peeper is a small, yet fast, passive fauna species that could be considered the mascot of Subnautica. It is easily identified by its large, bright yellow eyes. The Peeper will try to flee from most life forms larger than itself, such as Stalkers or the player. They can be caught, though their speed allows them to easily outrun a poorly equipped player. With the use of a Grav Trap, Seaglide, Stasis Rifle, or Propulsion Cannon, they can be easily captured. To catch them without any tools it's easiest to approach them from above.

Attitude: Passive
Edible
Food Value: +44
Energy Value: +490
The Reginald is a common, passive, herbivorous fauna species. Cooked and cured Reginald have the highest food value of any fauna, making them an excellent food source. The Reginald is fast and is mostly seen darting around the open space in various biomes, tending to live solitarily. They can often be found swimming around the pillars in the Grassy Plateaus. It is also a shy creature and will eventually flee from the player upon being noticed.

Attitude: Agressive
Health: 8000
Damage (Adult):
-Bite: 84 (Player)
-Bite: 42 (Seamoth)
-Bite: 14 (Prawn Suit)
-Bite: 250 (Cyclops)
Damage (Juvenile):
-Bite: 55 (Player)
-Bite: 27 (Seamoth)
-Bite: 9 (Prawn Suit)
-Bite: 220 (Cyclops)

Adult Ghost Leviathans are the second largest creature in Subnautica. Juvenile Ghost Leviathans measure at around 63% the size of a mature individual living within The Crater, but despite this, they retain the same amount of health as their adult counterparts. However, juveniles deal 34.5% less damage. Three Ghost Leviathan Juveniles spawn on the map, all within the Lost River biome. Three adult Ghost Leviathans spawn on the map (not counting the infinite number found in the Crater Edge): two in the Grand Reef, and one in the Northern Blood Kelp Zone.

If the player enters the Crater Edge, a single adult Ghost Leviathan spawns in. If the player stays in the Crater Edge for 40 seconds, a second Ghost Leviathan will spawn. If the player stays in the area for another 40 seconds, a third and final Ghost Leviathan spawns in. When/If the player kills them, they will respawn. They will all pursue the player until the player returns to the playable area, upon which they will all retreat.

To attack a target, it will spiral up and charge. When charging, it will open up its mouth and make a loud, echoing screech. If it successfully attacks, it will do 84% damage to the player and swim some distance away, as if losing interest. Juvenile Ghost Leviathans only do 55% damage to the player. Adults are able to push the Cyclops and either drag it, or overturn it. If the player is walking around the Cyclops when the Adult begins to push (for example, if they are trying to put out fires caused by an attack), and the Leviathan rolls the submarine over, the player can be killed instantly upon colliding with the walls or ceiling. When killed, the Ghost Leviathans that are within the Crater do not respawn. However, the adults that reside within the Crater Edge will continue to respawn.

Attitude: Agressive
Health: 5000
Bite:
Player: 80
Cyclops: 220
Seamoth: 40-60
Prawn Suit: 20-30
Grab:
If the next attack were to kill the player, this will be performed instead.

The Reaper Leviathan is an aggressive leviathan class fauna species usually found swimming in large open areas, such as the Crash Zone, Dunes, and Mountains. It is the third-largest aggressive creature in the game and fifth largest overall. Reaper Leviathans are the most populous species of leviathan, with a total of twenty-five roaming The Crater: nine in the Crash Zone, eight in the Dunes, seven in the Mountains, and a lone one on the edge of the Bulb Zone. One can be found lurking around the base of the Mountain Island.

The Reaper Leviathan emits loud, echoing roars audible from great distances. According to the data bank entry, this roar is a form of echolocation, though it does not function like this in-game. It also seems to circle its prey (or more commonly the player) for some time before attacking and often strikes from behind by surprise. The Reaper Leviathan often swims deeper down but not quite at the seafloor. Players can use this to their advantage and swim on the surface to avoid detection. It is also less likely to notice the player if they use a Seaglide instead of a vehicle. When the Reaper Leviathan is exposed to damage, it will flinch and roar shortly after. Like other leviathans, the Reaper Leviathan will not respawn if killed.

The Reaper Leviathan is capable of taking away 80% of the player's health if they are attacked outside their vehicle. Wearing a Reinforced Dive Suit will reduce damage taken by half, taking 40% damage instead of 80%. If the next attack kills the player, it will hold its victim in its mandibles, pause for a second while roaring, and then proceed to pull the player into its mouth, killing them. It is also capable of grabbing the Seamoth and shaking it around. Doing so will deal about 40 - 60% damage over eight to thirteen seconds until it lets the vehicle go. However, if hit with the seamoth's Perimeter Defense System, it will let go instantly. The Reaper Leviathan will also grab the Prawn Suit. If it succeeds, the damage incurred will only be around 20-30%. Even in Creative Mode, Reaper Leviathans will still jumpscare and grab Seamoths and Prawn Suits.