Request Identify Yourself Sea Power
You get a new unknown contact in Tactical Display, what do you do? Well you can request it to identify itself.
Do this from the tactical display, select the unknown unit, then (I assume) RMB click and choose Request: Identify Yourself. If the unit doesn't respond you will see a "system message" in the bottom center of the screen. PMCTODO
In the far left bottom of the screen you see white flag with question mark on it, this designates unknown contact/unit.
When you RMB click unknown unit you get to select; Friendly, Neutral, Hostile, Information and this Request: Identify Yourself.
Friendly means no shooting, no hostilities. Neutral means kind of like nothing, "forgetta 'bout it...", its no concern to us, neutral doesn't necessarily mean civilian though, it could be a military unit but simply neutral towards your country. Hostile means guns out, shoot him before he shoots you. Information is... I have no idea. PMCTODO
When you request identify yourself it doesn't mean all units automatically snap into attention and send you a full briefing who they are and what they are doing, as many aircrafts/ships might not be even listening to the same radio frequencies you are (I'm just speculating here, who knows maybe there are some international maritime LAW which dictates that you have to monitor some specific radio frequency). I've seen several youtube videos where this request falls to a deaf ears, no replies. Do not declare such unknown contact as hostile because it could be a simple civilian airliner/ship who is just not receiving your request. Only shoot what you have positively identified hostile.
Unknown contact can be seen in tactical display but it wont show up in 3D world because you don't know what type of unit it is. With unknown contacts it looks like your weapons hit invisible objects, this is normal.