[holohw]

Originally Posted by PanicEnsues

The blue circle shows the current range at which you can detect enemies; either visually (bridge spotters/periscope) or with sonar. The range starts at a maximum of 6000 m, then is modified down by various factors including weather, day/night, submersion, etc.

You can change that starting max range using the game's built-in modding editor (from the main menu, Options->Modding), under Game Vars/World/Max Visibility Distance. Note that the enemy spotters use that same variable, so changing it will also change the distance from which they can spot you!

Thank you!!