About this detail of the Tiger
This diagram [4, see page 23] shows the flow of cooling air in a Tiger 1. Hot air from the gearbox cover was blown over the exhaust pipes to gather more heat, then into a box on the rear wall of the vehicle. From there the main fans sucked it through pipes into the fan ducts.
During underwater travel, the main fans did not work and the sponsons were flooded. Air flow had to be redirected. As the diagram shows, there were butterfly valves ("Drosselklappe") in the pipes leading from the box to the sponsons. These were normally kept open. Also, a vertical pipe going upwards from the box had a valve near the top. This valve was normally kept closed.
Before underwater travel, all these valves were switched. The hot air then entered the engine compartment from the vertical pipe.
All three valves were controlled by a handle on the front left of the firewall. This photo  shows the handle in a tank built in mid 1943. Two curved bars with teeth are welded to the firewall; the handle clicks into these teeth and they hold it in position. (The air vent has been sealed up because experimental equipment is installed in this vehicle.)
The Tigerfibel states [4, see page 21] that this handle "leads the hot engine air to the fans or into the engine room". The positions of the handle are here marked "Zu" and "Auf". But in the earlier vehicle at Bovington museum  , there were hand-written words on the firewall: "Landfahrt" and "Wasserfahrt", meaning "Land travel" and "Water travel" respectively.
On the rear side of the firewall, the control cable ran across to the right-hand side wall, and along the top of that wall to the rear of the compartment.
The cable looped over the top of the right-hand fan clutch unit, and connected to an arm on the right-hand outlet pipe. This photo  shows the Bovington vehicle under restoration. The clutch unit is missing, and the cable is disconnected. The connecting arm is at the lower left of the photo. It is fixed to the axis of the butterfly valve inside the pipe.
The arm also moves a rod that controls the valve in the vertical pipe.
There is another arm at the rear end of the valve's axle, moving a rod that runs across the inside rear wall of the vehicle to the outlet pipe on the opposite side.
In May 1943, the Tiger's engine was changed to a HL 230  . There is a surviving technical drawing  that shows how to do the upgrade. None of these mechanisms are illustrated in the drawing, so they were not affected by the change.
In September 1943 the submersion capability was dropped from the Tiger's design. Many items were deleted from the vehicle, including these mechanisms. This photo  shows the situation after the change. (The vehicle is the Sturmtiger at Munster museum. Colours may not be original; the engine is missing.) The box on the rear wall was now manufactured without the vertical air pipe. The outlet pipes to the sponson were still present, but the hole for the valve's axle was sealed up.(The latest version of this article)