There are significant community discussions regarding the game's save system, particularly for Single Player mode: Progress Reset
Because of the lack of a formal save button, some players use built-in developer commands to quickly regain their progress. For instance, holding L while pressing U can level up your fish, effectively acting as a "cheat save point" to return to a previous state. Troubleshooting Save & Launch Issues feed and grow fish save file
/steamapps/compatdata/429050/pfx/ .
If you are moving to a new PC or want to prevent progress loss from file corruption, you should manually back up these files: feed and grow fish save file
If you need to manually backup your profile data or cloud saves, you can typically find them in these directories: feed and grow fish save file