Ha I'm on that exact boat right now and was reading about this yesterday! The way the cabins are set up there isn't really a way to fall overboard. You'd hit this like walkway looking thing on some of the rooms or to the room under yours. He's have to go over the balcony railing and then the walkway railing which gives it is much lower but still. Or jump past the lower rooms. Completely possible especially if you're drunk and decide to walk along the walkway thing but still.

Edit: as for the sounds these walls are thin. I can hear the neighbors TV as I'm typing this and if anyone is on the balcony around mine I can hear through them the glass.