Saves & config
Subnautica Save File Location
Subnautica keeps its saved games in [Subnautica install folder]\SNAppData\SavedGames on Windows. Copy the whole folder to back a save up; paste it back to restore it.
Save games
1Windows
Unusually, this one lives with the game rather than in your user folder — in Steam, right-click the game, Manage, Browse local files. A reinstall can take the saves with it.
%APPDATA% style variables expand to your own account, and it works
even though AppData is hidden.
Backing a save up properly
Close the game first. A save folder copied while the game is running can catch a file mid-write, and the copy then loads as a corrupt save weeks later when you need it.
If the game uses Steam Cloud, close Steam entirely before restoring an old folder. Steam compares timestamps on launch and offers a choice between the local files and the ones on its servers; restoring while Steam is open often means the cloud copy quietly wins and the folder you just put back is overwritten.
Before you try a cheat
Back the save up first. Some codes on the Subnautica cheats page disable achievements for that save file, and a few cannot be reversed once used. A copy of the folder costs nothing and undoes all of it.
These paths are written by hand rather than imported, and a game update can move them. If one is wrong on your machine, tell us and it will be corrected.
Quick answers
Subnautica saves
Where are Subnautica save files stored?
[Subnautica install folder]\SNAppData\SavedGames. Paste that path into the address bar of File Explorer and it will open the folder — the environment variables in it expand to your own user folder.