I'm a French citizen. In a recent trip to Ireland, I took a photo of an Irish military vessel entering the port.
By curiosity, I started checking whether it is legal to first take, and then publicly publish photographs of military vessels, but I can't find anything at all about the subject, neither for Ireland, nor even for France.
I suppose that since the vessel was visible from a publicly accessible area, there is nothing which would prevent even a foreign citizen from taking its photo and publishing it. However, the same logic appears to be wrong for instance for some of the French military bases which cannot be photographed even from the public area, or for any federal building in USA, or any strategic installation, such as the railway infrastructure, in Russia.
So what's the legal situation (either in general in European Union or specifically in Ireland)?
The photo makes it possible to see a lot of details such as the position of CCTVs on the vessel, the emergency equipment, etc.
The canons are covered, but a specialist can still easily guess their size and type.
The photo makes it possible to deduce that at a given time, the vessel was at the specific GPS coordinates.
Sailors are visible, but not personally recognizable.
The name/ID of the ship is not visible on the photo.