Subnautica Wiki
This article is about Rockgrubs in Subnautica. Click here for information on this subject in Below Zero.

The Rockgrub is a very small, passive fauna species that mostly dwells in cavernous areas. Despite superficially resembling an invertebrate the PDA states that it is a possible relative of the Sand Shark, meaning it must be a small vertebrate.


The Rockgrub is tiny in size, its translucent body glows a bright bioluminescent green color. It lights up a small spherical area around itself. It has a slim, round, segmented body with two swimming fins on either side, and a larger flipper serving as the tail.

The Rockgrub has five appendages on each side of its body, and a circular maw containing many small teeth.


The Rockgrub's small size would allow it to consume small bits of coral or vegetation clinging to the cliff faces that surround its habitat, as well as corpses or debris that float past it. It is unclear in-game if the species is subject to predation, however, the Rockgrubs can be seen evading larger organisms. A powerful tail gives Rockgrubs the ability to move quickly in linear directions, but are slow to react when turning because they lack dorsal fins and a horizontally flexible tail. Like other organisms in the mountain biomes, Rockgrubs have a chitinous plating around their bodies, forming a bioluminescent exoskeleton around their internal organs. This bioluminescence seems to light up the area around them, possibly aiding in finding food, but their lack of visible eyes indicates that it is a vestigial mutation not used by the current population. Alternatively, the eyes may be extremely small and almost invisible in this species.

Data Bank Entry

Rock Grub.jpg

A small, luminescent scavenger, roughly thumb-sized. This creature may be a distant relative of the sand shark, sharing that species' unusual limbs, segmented exoskeleton, and burrowing behavior.

1. Jaw:
Its circular set of teeth is designed to tear up clumps of coral and seagrass caught on the rocks.

2. Limbs:
Five legs, two arms, and a large flipper allow the rock grub to cling to and walk across rock faces in search of food, and swiftly swim to safety when under attack.

3. Green Luminescence:
Glowing green in the dark would seem like a poor survival strategy, but this adaptation may be a mating behavior or other specialized process, engaged in by only a fraction of the total population at any one time. Or perhaps being eaten is simply part of the rockgrub's lifecycle.

Assessment: Harmless



  • Code in the shared assets refers to the Rockgrub as the Rock Puncher Larva. By contrast, an early Trello card refers to them as "RockPuncher Food".[1]
  • Rockgrubs are the smallest Fauna in Subnautica.
  • At night, it can be difficult to see the actual Rockgrub because of its extremely bright bioluminescence.
  • The Rockgrub is the only fauna to make a glow that can actually light up the surroundings.