This is a picture of the bridge access trunk, taken while standing above the hatchway from ops upper level where the lower hatch goes to the control room. There is nothing here but junction boxes, the ladder and the light switch, and the tunnel is sheathed in smooth sheet metal (you can see the reflection of the light from the hatch on the right). The top hatch is open while running on the surface, and the officer of the deck stands on grating placed on top of the hatch. You can see beneath your toes 25 feet to the deck of the control room. The box at the top of the ladder is the bridge communication box, a toaster-sized console that has all the communication circuits and microphones and telephones, for use by the officer of the deck when conning the ship on the surface. The plug visible is an extension cord to make the bridge communication box be mounted down on the deck so the deck sentry can talk to the watchstanders belowdecks.