Planet 4546B
Planet 4546B is the uncharted ocean world where the original Subnautica and Below Zero take place. It is a water-covered planet in the Ariadne Arm of the galaxy, designated only by its catalog number. The planet's surface is almost entirely ocean, with a few scattered islands. Subnautica 2 takes place on a different planet, Planet Zezura, but 4546B's events and lore provide context for the sequel.
Geography
The playable area of the original Subnautica sits within a volcanic crater approximately 2 kilometers in diameter. The crater is surrounded by the Crater Edge (also called the Dead Zone or Void), an open ocean expanse with no floor and no resources, patrolled by Ghost Leviathans that attack anyone who ventures beyond the map boundary.
Depth ranges from the surface to approximately 1,700 meters in the Lava Lakes, the deepest accessible point. Two explorable islands exist: the Floating Island (buoyed above the water by Ancient Floaters) and Mountain Island (home to the Quarantine Enforcement Platform).
Biomes
Planet 4546B features over 20 distinct biomes, each with unique terrain, resources, creatures, and visual identity. The biomes are arranged in a roughly concentric pattern with shallower, safer biomes near the surface and progressively deeper, more dangerous environments below.
Biome | Depth Range | Notes |
|---|---|---|
Safe Shallows | 0-40m | Starting area around Lifepod 5. Abundant basic resources. |
Kelp Forest | 30-160m | Towering creepvine plants. Home to Stalkers. |
Grassy Plateaus | 80-170m | Flat terrain with red grass. Common Seamoth fragments. |
Mushroom Forest | 120-250m | Giant mushroom trees. Cyclops fragments found here. |
Blood Kelp Zone | 200-500m | Dark, foreboding biome with red bioluminescent kelp. |
Grand Reef | 120-480m | Deep reef with Crabsquid and Ghost Leviathan juveniles. |
Dunes | 180-420m | Sandy expanse patrolled by 8 Reaper Leviathans. |
Lost River | 550-900m | Cave system with brine rivers. Disease Research Facility location. |
Inactive Lava Zone | 900-1,300m | Volcanic caverns. Sea Dragon Leviathans. |
Lava Lakes | 1,300-1,700m | Deepest biome. Primary Containment Facility and Sea Emperor. |
The Kharaa outbreak
Planet 4546B was the site of a catastrophic Kharaa Bacterium outbreak. The Architects brought the pathogen to the planet for study approximately 1,000 years before the events of the game. A containment breach at the Disease Research Facility in the Lost River released the bacterium into the planet's ecosystem, infecting wildlife and eventually the player. The Sea Emperor Leviathan's offspring produced Enzyme 42, which cured the entire ocean.
Architect presence
The Architects built four major facilities on 4546B: the Quarantine Enforcement Platform (Mountain Island), the Disease Research Facility (Lost River), the Alien Thermal Plant (Inactive Lava Zone), and the Primary Containment Facility (Lava Lakes). These structures contained alien technology, data terminals, and the imprisoned Sea Emperor. The QEP shot down any spacecraft attempting to leave or approach the planet, trapping Ryley Robinson until he cured the Kharaa and deactivated the weapon.
Human activity
Three human expeditions reached Planet 4546B:
Expedition | When | Outcome |
|---|---|---|
~10 years before Subnautica | Ship shot down by QEP. Three survivors built bases at increasing depths. Two died; Marguerit Maida survived. | |
During Subnautica | Alterra Capital Ship shot down by QEP. Ryley Robinson was the sole surface survivor. He cured the Kharaa and escaped. | |
Alterra research operations | During Below Zero | Alterra returned to Sector Zero for research. Robin Ayou investigated her sister's death. |
In Below Zero
Below Zero expands the explorable area of 4546B to include Sector Zero, an arctic region far from the original game's tropical crater. Two years after Ryley Robinson's escape, Alterra established research stations in the region. The environment includes ice sheets, glacial basins, underground cave networks, and deep-sea volcanic vents. Marguerit Maida from the Degasi crew has established a self-sufficient homestead in the area.
Connection to Subnautica 2
Subnautica 2 takes place on Planet Zezura, an entirely different alien ocean world. No characters, creatures, or vehicles from Planet 4546B appear in the sequel. The connection between the two planets is maintained through the broader universe: Alterra Corporation's ongoing activities, the Architects' ruins found on Zezura, and the Voices From Beyond audio drama that bridges the previous games and the sequel.