Why submarines are not automatic superweapons

Are submarines really superweapons capable of wiping out an enemy surface navy?

They are powerful but not automatic winners; competent anti-submarine warfare and wartime freedom to prosecute uncertain contacts change the balance.

Submarines have been marketed as decisive stealth weapons since the earliest practical experiments. Their real effectiveness depends on the opponent's anti-submarine forces, operating procedures, and freedom to attack uncertain contacts. Exercise rules can make submarines appear stronger because peacetime participants cannot treat every ambiguous sonar return as hostile. Wartime commanders may use explosives against any plausible contact, accepting risks that would be forbidden in an exercise.