Going through some on-line records of the Royal Navy 'Communicator' magazine for the communications branch I came across an article from the xmas 1963 edition. Like the RN, the USN allowed amateurs to operate on board ship. The article refers to the USN amateur radio club/association. For simplicity I've edited it a bit. This must be one of the rarest QSOs between Hams, and made from a very unusual QTH(Position):- ".....there are 260 active amateur stations onboard USN ships.......including the US submarine Tusk.......one recent QSO (contact) was when K4CSY/MM was crossing the Atlantic and the QSO was conducted when she was operating at a depth of 65 ft!!' NB ' a submarine can release a buoy with a small vertical aerial to communicate whilst submerged. All the editions of the magazine can be accessed here. https://www.commsmuseum.co.uk/communicator.htm And there's a lot of stuff covering every aspect of morse code.