Go to the Tram Control room, the underwater room at the end of the long tunnel from the Nexus - you know, the one that shows a cinema sequence with the flashlight when you go through it. Go to the far left window and look out into the water. Boston will comment on the underwater tunnel. Now type 'SWANS' on the keyboard, and watch carefully! This doesn't affect anything game-wise, it's just a goofy little trick.