"Military" yacht?

Hi to all. I am new member from Dubrovnik, Croatia, and have a question to ask.
Are there any military-or-goverment-owned yachts out there? I'm asking this because of the picture I took a couple of days ago. The picture shows a fairly large yacht(about 70-80 meters in lentgh), coloured in military fashion and colours, with absoloutely no name, just a number on her stern(the number was 9906). The story is that she was to serve as dick cheney's yacht while he was visiting Dubrovnik. I have a picture of her, is it possible to upload it directly here, or should I send it to someone?