South African Ports vs. European and Carribbean

On our previous cruises we usually picked up a tour when we got off the ships in a port of call. The tours were generally at least comparable to what the ship offered, for less money, and most were quite good. This will be our first African cruise, and we are curious as to what will be available in South Africa - particularly Richards Bay, Port Elizabeth, and East London (I suspect Cape Town will not be a problem) - and Walvis Bay, Namibia as well.

Would appreciate any information/experiences.