In the world of Subnautica, you follow the story of silent protagonist Ryley Robinson, a crewmember of the Altera Corporation spaceship the Aurora. After the Aurora crashes into the alien planet referred to as “4546B,” Ryley ends up being the only survivor. Stranded on an unknown planet covered entirely in vast ocean and with no way home, you as a player must challenge 4546B’s hostile environment. To find your way off the planet and back to Earth, you must travel deep into the ocean’s great depths, unravel the mysteries of the mysterious alien race that came before you, combat the aggressive flora and fauna lying in wait for you, and race the clock as a deadly disease rapidly takes over your body.
4546B is the name given to the planet at the center of Subnautica’s story. 4546B is an entirely aquatic planet with only two points of dry land for the player to find. By the time the game begins, the planet is uninhabited, all other sentient life having perished due to circumstances that will be revealed to the player in time. Throughout the game, the player uncovers secrets of past inhabitants of 4546B and what led to their demise.
Though the planet is only occupied by aquatic life, there are still many great dangers within its waters. The player will encounter many dangerous creatures from the shallow waters of the surface to depths exceeding 2,000 meters. Battling not only the aggressive fauna, but hunger, thirst, and a finite oxygen source, there are many aspects to keep in mind when you choose to get your feet wet on 4546B.
The game's main area is located entirely within a small section of the planet dubbed the crater—only about 2 kilometers wide, the crater was likely formed from underwater volcanic activity. Beyond this small environment is an uninhabitable darkness called the Dead Zone, and the player is unable to explore further without severe consequences. Though the Dead Zone is a death sentence, there are still many dangers within the crater, posing a threat in even the safest of places of 4546B (see biomes and wildlife for more).
The Aurora is the great Alterra Corporation spaceship whose crash is the catalyst of all events that occur within the game. After drawing too close to 4546B, the spaceship is hit with a strange energy beam and ultimately crashes into the planet’s surface, killing all but a handful of the ship’s inhabitants. Thanks to its size, the Aurora is often the only visible above-water landmark. It’s visible from nearly every point of the planet, and the player begins their journey only a brief swim away from its crash site.
The Aurora is one of the first threats the player faces – after its Drive Core overheats and finally explodes, the ship begins to leak radiation into the water, which will kill the player and lead to a mass-extinction event unless the damaged Drive Core is repaired. Even after the player is successful in eliminating the radiation, the Aurora remains a danger. With reaper leviathans that patrol the exterior of the ship and parasitic bloodsuckers that infest the interior, drawing near the ship is a risk. Even if the player chooses to keep their distance, what’s left of the Aurora remains, a constant reminder of what landed Ryley Robinson here in the first place.
Ryley Robinson was not the only survivor of the Aurora crash, but he is the only one who does not succumb to 4546B’s hostile environments—throughout the game, you can come across a series of destroyed lifepods of your fellow Auora survivors. You are never able to find the actual survivors, as they've perished by the time you regain consciousness within your own lifepod. But through environmental clues and recordings left behind, you can piece together what happened to each survivor and why you survived when they didn’t. Were they unlucky and got stuck in a faulty lifepod? Did they land in a biome with highly aggressive leviathan-class predators? The more you explore, the more lifepods you find, and the more you understand the fates that befell your former companions.
After crashing and beginning to explore their new underwater world, the player will soon notice some of the aquatic wildlife doesn’t look particularly healthy—some of the fish the player encounters are covered in unusual bright green pustules that seem to pass from host to host. This is the Kharaa bacteria, a terribly infectious disease that has spread across all of 4546B. Through their adventures, the player will discover that 4546B is under quarantine because of this bacterium; any spaceship that draws too close to the planet will be gunned down to prevent infected hosts from escaping and continuing the spread. Soon, it isn’t just the fish who are showing symptoms; the player has contracted the Kharaa. In order to cure themselves and escape the planet, the player must find a cure and eradicate the bacterium from 4546B.
The Architects are the alien species that inhabited Planet 4546B a millennium before the game takes place, and they are long gone by the time the game’s storyline begins. The player is able to discover that they were searching for a cure to the Kharaa virus and were unsuccessful in doing so. The Architects might still be out there, but they were forced to evacuate the planet and abandon any infected after their research facility was attacked by leviathans. Though they never appear in-game, the Architects’ influence is everywhere on 4546B. You are able to explore their abandoned facilities miles underwater and utilize their ancient technology for equipment upgrades and information.
The Aurora is not the first earthling ship to crash land on 4546B; throughout the game, there are signs that point to a different spaceship, the Degasi, crash landing several years before the game begins. The player can discover the Degasi crew’s different bases and audio recordings that give them information on who the crew was and what they faced. Though the Degasi never made it back home, their extended survival is a point of hope for Ryley Robinson and the player; if they can last as long as they did, maybe you can too.