Having just returned from a trip to the Cape ....
And considering that the geocachers in that neck of the woods have a insatiable penchant for placing caches on top of mountains and in inacessible caves, and also on narrow ledges with half a world of air between you and the ground. ..... then another one just 161m away that requires a 3 km hike to get to.
But seriously ...
Silvermine is a great area and there is at least a morning's worth of good caching to be done (if not a full day). The walk from the Silvermine parking area to Sentinel View is about 2.5km straight line and is so worth it. For the exercise, the views and of course SA's oldest cache.
Be warned. Fynbos is a total misnomer and it is anything but "fyn". I still have scratches on my legs. Rofbos is a better name.
The section of road from Fish Hoek to Cape Point is rich in caches, most of them easy-ish - helps with some numbers.
Just my 2c.