A sub is too stealthy, you need high profile muscle-flexing like a carrier group or two. Makes tyrants shut up, which is probably why the big E is near Iran. It'll keep them quiet and out of the headlines in the runup to the elections.
But they can let themselves be seen if they wish. An Ohio class SSGN cruise missile/spec ops boats surfacing just outside your 12 mile limit will get your attention. Then when it's sure it's been spotted, it will slide below and disappear, possibly to appear again somewhere else. Or that may be the only time you see or hear it. Is it gone? You decide. :)
Of course it can be pretty "gone" and still hit you with those cruise missiles. :)