From ROI Wiki

The Calypso is a Balao class salvage submarine that doubles as a combat vessel whenever needed and includes a remote controlled auto reloading 80mm twin barrel deck gun, and two torpedo tubes. She is the fourth in her class of 17 ships, and one of the most distinguished out of them all. She is skippered by Clifford Weiss and is one of three ships that employs recovered controller technology, including a quantum power core and map table. The other two are the Thor and the Odyssey. Originally a diesel electric submarine, she was later refitted with the controller technology and put to use handling the more difficult jobs that the other submarines couldn't perform. The advantages of these upgrades are unlimited range and longer linger times on station, allowing the ship to more easily locate and collect more salvage than the other ships in their class. The home base for the submarines is the submarine shipyard of Subton.