Subnautica: Mountain Island - biome guide Subnautica Guide and Walkthrough
Last update: 27 March 2021
The second surface island biome. Its also the highest peak in the games mountain area.
Truth be told, the only point of interest on the island in the vast Alien Facility. Reaching it is possible only after we've acquired the Purple Tablet. It can be found, e.g. in one of the abandoned bases on Floating Island. Placing the tablet on the special pedestal will open the facility. Inside, you'll find numerous alien data files and several Ion Cubes. Other than that there's only some sandstone and shale.
The island itself is a safe area; except for some Cave Crawlers you won't encounter anything truly dangerous. Also the alien facility is completely safe to explore. The only thing you may have to watch out for is the Reaper Leviathan that patrols the northeastern shore of the island.
In short, the Mountain Island is yet another location to be visited only once. Once you've explored the alien base, it will provide only common, basic resources, to acquire which you'd have to avoid a Reaper Leviathan - not a good deal.