You have to swim underwater and grab a key from a dead ghoul; there are two of these (two dead ghouls and two *different* keys). Then find a terminal in the area. Use one of the keys to open the water pump valve. This will make the area with the second ghoul a different area, but opens an unaccessible area. Follow that and find a computer where you use the second to open the Overseer's office. Exit back to the first area and enter the Overseer's HQ and progress to the office. An orange ghoul will be standing atop. Kill him for the key or hack a very hard terminal to open the armory.
Inside the armory are two ghouls but that should be nothing by now. Also, entering below the overseer's office will allow you to end a quest (that you may have gotten earlier or started in Vault 34 like myself).
overseer has a key but its 4 the reactor downstairs 4 the quest, not the armory door so im assuming that the very hard terminal in overseers office is the only way wich suks cuz i cant open it at this point