Ferry commuter and the real deal!
Hi, I ride the Minnesott-Cherry Branch ferry 2X a day. I had asked the same question and it was explained when the Fed's setup their checkpoint there occasionally, vehicle search, etc. by DHS and TSA they are surprised how well armed the citizens of NC are! If the weapon is concealed and you have a CCW, they don't and cannot do anything against you and the same is true for OC!
I've OC'd many time while riding the ferry and just left it on the dashboard while riding across. (I remained in the drivers seat)
I engaged the security in small talk and he said that OCing was fine, and it's your right to OC in NC as long as it's visible. They have no problem with it at all.
And there is NO SIGN banning firearms, at least on the ferry I take.