Yangtze The Yangtze - 31 ( Chinese : 扬子 - 三十一 ; ) , is a Chinese nuclear - powered ballistic missile submarine commanded by Zao . When first discovered by the Sole Survivor in 2287 , it is lodged in the shallow waters off the coast of the Commonwealth south of Boston Airport and northeast of the Four Leaf fishpacking plant . The submarine is not marked on the map until the Sole Survivor swims out to it . Upon discovery , the quest Here There Be Monsters will automatically be started if it hasn ' t been received already from Donny Kowalski near the Shamrock Taphouse . Background . Sometime before the Great War , the " Yangtze " was sent on patrol along the U . S . Atlantic coast with a payload of six strategic nuclear SLBM s and an uncertain number of tactical nuclear missiles and torpedoes . It is unknown if the vessel experienced any combat prior to the Great War . When the Great War began , the " Yangtze " < nowiki > ' s < / nowiki > captain obeyed his orders to fire the submarine ' s strategic nuclear weapons at their targets . All but one of the missiles were successfully launched . Shortly after firing its strategic missiles , the " Yangtze " struck a mine that severely damaged its reactor and forced it to seek shelter in a nearby harbor , which just so happened to be the port of Boston . The damage caused a reactor leak that immobilized the sub and ultimately killed or ghoulified the crew of around 23 men , of which only Zao retained his sanity . Layout . The " Yangtze " is a unique design for a ballistic missile submarine . It has three large propellers located on either side and under the reactor control room , as well as a smaller propeller at the rear of the sub with the rudder . The sub ' s design is unique as all of the facilities and machinery are located fore of the conning tower , which sits halfway on the sub , with only a small propeller and the rudder being behind the conning tower . The first room the Sole Survivor comes to when entering the submarine is the control room / bridge where Zao is located . Down the stairs is the reactor control room with a radio room on the port side ( left when facing forward ) . There are two doors on either side of this room that go to a small room with a cage wall and a large machine behind which is presumably the propeller drive shaft . Behind the reactor room and under the bridge is a room with the machinery and instrument panels . On the port side of the room is Captain Zao ' s quarters and on the starboard side is the officers mess . Forward of the reactor control room is the upper reactor level and contains the reactor access hatch and a stairway , on the port side , leading to the lower level . The lower level contains reactor machinery and two doorways , at the rear , leading to the engine room for the lowest of the large propellers . Past the reactor room on the upper floor is a small room that contains two decontamination showers and a locked door with a stairway to the lower deck . There is also a science lab on the port side of the room . Forward of that room ( still on the upper level ) is the sub ' s mess room , galley , and food storage ( the room opposite the galley ) . Forward of the mess is the crew quarters , containing 80 beds ( configured in 8 stacks of three and 14 stacks of four ) , the sub ' s lavatories and a laundry room ( port side ) , as well as the ships med - bay / infirmary ( starboard side ) . At the front of the quarters are two doorways that lead into each other at the front of the sub , then lead into a room on the lower deck that contains machinery with a workshop on the starboard side and a storage room on the port side . The next room contains a doorway on the starboard side leading to the sub ' s armory , and a hallway at the end leading to the silo room . The silo room contains the 6 missile silos with 3 along each side . Each silo has an access hatch that allows the crew to access the SLBM inside . All are closed except the one with the missile that failed to launch . The next room is a small room before the reactor room which contains a locked door to the upper level . Unlike the only other Chinese submarine the player character can personally encounter in the series , SSN - 37 - 1A , the " Yangtze " is in fact a full - scale combat vessel with extensive crew amenities and visible missile and torpedo tubes . It is shaped very differently to any real - world submarine , unlike the SSN - 37 - 1A , which bears a very conventional ( albeit small ) design . Appearances . The " Yangtze " only appears in " Fallout 4 " .