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An unfinished flora species found in the Glacial Basin.

The Glow Fungus are currently the only biophosphorescent organism in Subnautica: Below Zero.

Player can use Flashlight or Headlamp to illuminate them and they will light up in the dark cave.

Databank Entry

Glow Fungus

The Glow Fungus is commonly found in dark caves, and is marked by its exhibition of biofluorescence - a unique ability to absorb and emit electromagnetic radiation.

This is not to be confused with the process of bioluminescence, which many underwater lifeforms exhibit on Planet 4546B. Bioluminescence is a chemical reaction caused by the molecule luciferin when exposed to oxygen.

Source: Scan Glow Fungi