The official Steam build of Subnautica is currently on version 71399 or higher (depending on the "Legacy" branch). Applying the old V71288 update to a modern save file will instantly corrupt it. The game will load, but your base, vehicles, and story progress will vanish.
Greatly increased the speed of ascent when using the Air Bladder, making it a viable emergency tool. 3. Performance & Technical Fixes Subnautica V71288-P2P UPD
If the build includes a Steam emulator (like Goldberg or CODEX), ensure the Steam_api64.dll is present in the Save Compatibility: The official Steam build of Subnautica is currently