The Tiger could be completely sealed for deep wading. The seal for the joint between the gun and mantlet is shown in this sketch from the Turret Manual. For clarity, the gun tube and cradle are not shown.
The Cradle Seal ('Wiegenabdichtung') is located at the end of the gun's bearing sleeve. This puts it inside the mantlet, inaccessible from within the tank. Therefore it is manipulated via two arms, adjusted via levers and a handwheel.
This diagram from the Turret Manual shows the left side of the gun cradle. You can see that the levers are mounted on the cradle, with the arms passing along the sides of the gun bearing sleeve.
This view from above shows how the seal works. A rubber ring ('Dichtring') is carried loose on the gun tube. Ahead of it is a fixed ring, and behind it is a large movable cylinder.
By turning the handwheel, you can force the cylinder forwards. This squeezes the rubber part against the fixed ring, expanding it to form a tight seal between the gun tube and the outer protective sleeve.
This is a cross-section of the cradle, looking forwards. You can see that the levers and arms tightly straddle the gun sleeve. The levers are hinged in mounts welded to the lower wings of the cradle.
Note that, in order to fit the arms between the gun sleeve, the recuperator and the buffer, this part of the gun sleeve is narrowed. This is because the deep-wading equipment was added to the Tiger's design at a late stage.
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 list of procedures for sealing the turret.
This is the Late Tiger of Saumur museum. We are looking at the top of the gun cradle. The deep-wading ability of the Tiger was deleted in September 1943, long before this tank was built. The handwheel, the levers and presumably the seal are therefore not present in this tank. But it is clear that the cradle drawings were never updated. The slots for the arms, and the welded base for the handwheel, are still present.