Fictional organisation A wants to effectively fake military presence at sea - a remote location far away from any civilization, trade routes, radar/sonar stations. The target is a single civilian vessel B (e.g. a research expedition) which is in sight range and can be contacted by radio or optical signals.
Organisation A has considerable ressources - of course not enough to aquire (or legally own, for that matter) a military craft outright, but enough to get a ship sized like a patrol vessel, fast attack craft or corvette at maximum and make it look like an existing ship of that class with quite some detail, but without or only a bare minimum of functional military equipment/weaponry (they might be able to fake a warning shot), a prop basically.
They have trained crewmen at their disposal, which are - although real sailors - no actual soldiers, but can convincingly (for a civilian observer) pretend to be. The identifying transponder of the ship will be turned off (common practice for military craft) and A can effectively argue that they won't turn it on just for identification as this would disclose their precise position.
E.g. Organization A claims to be the USS Ardent, identify themselves as such via radio and make certain demands (aka move out of a specific area). Civilians B suspect that A might not be military but certainly don't want to risk pissing off the real US Navy who might just blow them out of the water if they dont comply.
B of course have no clue regarding the whereabouts of the actual USS Ardent. If they google for pictures, those will pretty much match the size, shape, ship, displacement etc. of what they can see. If B look closer, they will be able to see the correct flag and a plausible amount of crew in their respective uniforms. There are no obvious "rookie mistakes" to be discovered or details to spot for a civilian which could blow the cover. In short, B must rely on outside verification.
Is this level of illusion even feasible to achieve/maintain with the means described? If not, what is lacking?
Is there even any possibility to get confirmation or falsification on the identity of the ship that claims to be the USS Ardent from either the US Government or Navy? They probably won't hand out the position of their warships - and who would you even call to ask...?
Hey, we have encountered the USS Ardent at [position], is this the real one and actually your ship?
If yes, is there a standard procedure to follow (i know there is one for individual soldiers) and how long would that take?
Answers regarding the US Navy are most appreciated. However, if you know the answer for the naval forces of a different country, im interested to read those as well.
Parts of this question are worded in some way that might give a wrong impression. I might have exaggregated the aggressive behavior or possibility that the US Navy opens fire on civilians. This is not the case however, the demands made by A are not out of this world, more a minor inconvenience in the sort of Please navigate around this area for your own safety. It is actually not important, neither for A or the question itself, if those demands are actually followed by B or not. The main goal of the con is making A believe that the US Navy operates at this position