In Subnautica, the player must survive on the secluded ocean planet, 4546B. Thankfully, since they'll spend so much time on it, the planet is far from boring. 4546B's oceans support a diverse collection of marine flora and fauna. Most creatures in the game are detailed and semi-realistic. At times, Subnautica can feel like a crash course in biology — and not in a boring way, either!
For many of us, discovering and cataloging new creatures is the best part of the game. After all, who else is going to explore this distant planet? These are the really memorable discoveries; the coolest, most interesting animals in the Subnautica series.
10 10/10 Stalker
Stalkers are an intimidating species of fish resembling a cross between a shark and a crocodile. They often bother the player as they explore the Kelp Forests. Stalkers can be very intimidating before the player gets their submarine since they tend to sneak up quietly, and a few of their bites will spell death.
Their databank entry notes that their "teeth are unusually hard, and fast-growing". They use titanium deposits to sharpen and remove their baby teeth. Scrap metal is everywhere in the Crater thanks to the crash, and the Stalkers really love it. Watching them playfully toss around bits of metal is actually cute, which is funny considering how scary they can be at first.
9 9/10 Reefback Leviathan
The Reefback is one of only a few leviathan-class species in the series that are totally passive. They can be strange at first, with their huge bodies and whale-like cries. However, the player will quickly realize they are gentle giants.
Each Reefback supports a miniature ecosystem of plants, barnacles, and coral. The plants take root in "scars" or gashes that form across the Reefback's chitinous shell. The presence of Reefbacks suggests a safe area. They generally stick to the shallows so they can better protect their young from carnivorous leviathans. After a while, their low drones become almost comforting.
8 8/10 Reaper Leviathan
The Reaper is likely the first carnivorous leviathan-class creature players will encounter in Subnautica. Reaper Leviathans look like gigantic eels with demonic horns and razor-sharp teeth. They're all over the Crater but tend to bunch up in certain areas (the mountains, the dunes, and the crash zone), meaning the player should regard these areas with extreme caution.
Although Reapers have a nasty tendency to sneak up on the player, they also telegraph their attacks with a screech. Noted in the Reaper's databank entry as a form of echolocation, the screech is well known among fans of Subnautica. It's the player's cue to get out while they still can.
7 7/10 Gasopod
The Gasopod looks almost mammalian, like a seal or a manatee, but it has this bulbous orb of poisonous energy hanging from its backside. It also has two big eyes and a cylindrical mouth, making its face look like an old-school gas mask.
As is mentioned in the Gasopod's databank entry, their large bodies provide "a substantial meal to would-be predators". As a result, Gasopods release "gas pods" for defense, which burst into underwater clouds of poison. This behavior is almost squid-like, and while Gasopods are not aggressive, they are dangerous. Players can be tricked by their cute appearance, and draw closer to scan them, only to get smacked in the face with poison gas.
6 6/10 Glow Whale
The Glow Whale is a passive leviathan-class creature, similar to the Reefback Leviathan. They look a lot like the baleen whales here on Earth. Glow Whales are absolutely beautiful, and not only that, the player can ride them!
Glow Whales seemingly evolved for deep, dark ocean areas. They sport tons of bioluminescence, with glowing eye glands, light blue horns, and lit-up spots all across their bodies. In addition to riding them, the player can even pet them. Their databank entry notes that the whales are communal, and they emit high-pitched noises when they're near other whales, out of joy. And that's just adorable.
5 5/10 Mesmer
The Mesmer is the smallest, most mysterious creature on this list. Mesmers hunt and defend themselves by hypnotizing their targets. Their powers corrupt even the player's databank, meaning information on their biology is sparse.
When the player encounters a Mesmer, their controls lock up, and their PDA starts telling them to "swim closer to that beautiful creature". Once the player gets in range, the Mesmer simply gives them a little bite and swims off. The encounter is very off-putting, especially since Mesmers are so rare, but it could be much scarier. These little fish are so small and unintimidating — they can't really hurt the player. A Mesmer Leviathan, on the other hand, would be bone-chilling.
4 4/10 Vent Garden
Vent Gardens are leviathan-class creatures that nest above geothermal vents in the ground. They feed on microscopic bacteria emitted from the vents, and they look a bit like giant jellyfish. By far the coolest thing about adult Vent Gardens is that the player can go inside them and swim around a bit. Each Vent Garden contains its own tiny ecosystem of rare plants!
The databank notes that Vent Gardens create a symbiotic relationship. The structure of the Vent Garden prevents smaller creatures from feeding on the plants inside. Meanwhile, the plants filter and absorb dangerous gasses coming from the vents. These types of mutual relationships occur between creatures here on Earth, so why not on 4546B?
3 3/10 Ice Worm
One of the most unique creatures in the series, the Ice Worm is subterranean rather than subaquatic. Instead of swimming, it burrows through the ground, attacking the player as they explore the ice sheets. It's a giant worm, like similar creatures from Dune, Shadow of the Colossus, etc. It can also jump and almost fly through the air, which is just as scary as it sounds.
The Ice Worm burrows through the hard ice using a superheated horn on its head. It has an intimidating appearance, as well as terrifying animations, including one where the player is tossed up in the air and into the Worm's mouth. It's very unique and catches most players off-guard.
2 2/10 Shadow Leviathan
The terrifying Shadow Leviathan stalks the depths of Sector Zero in Subnautica: Below Zero. It looks like a giant sea snake with a triangular hammerhead and mandibles surrounding its glowing mouth. Like the Glow Whale, the Shadow Leviathan is bioluminescent, making it (thankfully) easier to spot from a distance. Unfortunately, that won't be much help when this giant is barreling down at frightening speeds.
In addition to being one of the coolest-looking creatures in the series, Shadow Leviathans have interesting biology. Their aerodynamic heads and tail fins allow them to propel themselves with some realism. Their huge mandibles are reminiscent of arthropods, like crabs and lobsters. The databank notes that their glowing mouths attract phytoplankton, which in turn attract larger fish.
1 1/10 Ghost Leviathan
The Ghost Leviathans from Subnautica 1 are absolutely terrifying. These beasts haunt the outer rims and dark depths of the Crater. Their long bodies are translucent — a quality also found in some marine life on Earth, such as the glass squid. In low-light environments, being see-through means you are effectively camouflaged. From a distance in Subnautica's dark void, the ghost leviathans look just like their name — like ghosts.
Interestingly, Ghost Leviathans are filter feeders, meaning they consume microscopic organisms from the water. The databank notes that their attacks are territorial, "not predatory". Their hammer-shaped heads, which protect them during bash attacks, suggest that they are very territorial. Their amazing look and tendency to gang up in the dark void around the Crater's edge make them extremely iconic and memorable.