Don't freak out, I'm not a shill (read my submission history). Can you ID that vessel and location?  I can't.  The only known and named, seaworthy prison ship in the US I've been able to Id has been the Bain.  There was another one mothballed in the 90s, I think.  That's not to say it hasn't been recommissioned and made seaworthy + corrections certified.  That could be done under relative secrecy.    I watch the GMTO stuff pretty closely.  Everyone has been saying the Vernon Bain has been headed to GTMO for months.  So I called them and said I was going to see an old friend and I wanted to confirm the address for visiting hours and she did. I'm a realist.  I deal in facts.  What can be proven/dis-proven. Statistical probability. Etc.    FWIW, the Vernon C. Bain is not listed in the databases used to track the ADS-B transponders on ships: https://www.marinetraffic.com/ That means it must be tugged.  Find the ADS-B for your grey ship's tender, and you can track.