My wife and I spent the afternoon sandboarding with Swakop Sandboarding (African Style) and then went with them the following day on a township tour. Sandboarding (in fact nearly all outdoors adventures in Swakop) is usually done in the morning as the wind picks up in the afternoon, but they took us out at late notice for an afternoon from about 2.30 till 5. Our guide Costa was a great teacher and photographer and very interesting to chat to about life in Namibia.
The following day we went with his colleague Bambo on a tour of the Mondessa township which lasted from 3pm till 7pm. He was an extremely knowledgeable guide and it was a real insight into the racial segregation that is more or less hidden from tourists. We were able to visit families from each of the 4 main tribal groups and even had a lesson in the "click"languages before finishing off with a couple of beers and some food at one of the shabeens. Well worth it if you want to find out a little bit more about life in Namibia.