Mercy-class hospital ship
Appearance
The Mercy class of hospital ships are converted San Clemente-class supertankers now used by the United States Navy as naval ambulances. Two of them are used by today's Navy:
They are both maintained by the Military Sealift Command. They do not carry any ordnance, and firing on either of them is a war crime.
Wikimedia Commons has media related to Mercy class hospital ship.