In the top two photos, the water pump housing and the backing plate have both been removed. The gearbox has been partly dismantled and the water pump driveshaft has been removed to improve visibility. This was done for photographic purposes only - it is not necessary to remove or dismantle the gearbox in order to replace the water pump seals.
In the first photograph the outer (water) seal and the outer locking ring (circlip) have been removed. The inner locking ring and the inner (oil) seal are still in place.
In the second photo, a wire has been passed through the "indicator hole" in the bottom of the housing, to illustrate its location.
In the bottom photographs, below, the outer (water) seal has been refitted. The piece of copper wire again illustrates the location of the "indicator hole". It's easy to see in these photos, but don't be fooled - when the engine is installed and the coupling flange is in place on the propellor shaft, it is almost impossible to see without a mirror.