About this detail of the Tiger
The Tiger could be completely sealed for deep wading. The gun barrel could recoil; therefore a removable seal was required between the barrel and the mantlet.
It was not necessary to remove anything in order to activate the seal. That could be done from within the turret. The Cradle Seal ('Wiegenabdichtung') is shown in this sketch from the Turret Manual; a sliding ring on the end of the cradle could be pushed forward by two levers, with force applied by turning a handwheel.
This is the handwheel in the Bovington tank, before restoration. Under a layer of dust, its original colour is black. You can see that the levers pass through slots in the gun cradle. The handwheel carries the legend '5'; this is its number in the sequence of steps for sealing the turret.