Oxygen Tunic Creature Guide and Details | Subnautica 2

A strange glowing blue organism scattered across the ocean floor that emits oxygen bubbles.

Tunic aeolian. A bizarre animal that splits seawater into hydrogen (on which it feeds) and oxygen (which it releases).

[1] Tunic
Like Earthly tunicates, this is a complete animal with a heart, nerve cord, and a flexible exterior shell (the tunic).

[2] Radiolytic metabolism
At the heart of the oxygen tunic is a nugget of radioactive metal such as uranium, radium, or thorium. Radiation from this nugget splits water into hydrogen and oxygen through radiolysis. The oxygen tunic retains the hydrogen to feed an internal colony of sulfur-reducing bacteria, and releases the excess oxygen.

[3] Blue glow
Cherenkov radiation from the core excites radioluminescent pigments in the tunic, producing a distinctive blue glow. This may be a warning to would-be predators that the oxygen tunic releases poisonous quantities of oxygen.

[4] Implications for life on this world
The oxygen tunic's metabolism suggests that this world has an energetic geology and a biosphere adapted to use radiation as a food source. It also has interesting implications for life without sunlight. On Earth, even deep-sea vents depend on oxygen produced by photosynthesis. No such dependency exists here.

Assessment: emergency oxygen source for divers. Beware that repeated use could lead to radon buildup, with serious health risks including cancer.

Keep an eye out for Oxygen Tunics during deep dives! Swimming through their bubbles can refill your oxygen meter.