One of the most enjoyable activities in a desert is sandboarding, or surfing the dunes. Swakopmund is in the Namib Desert where several companies offer this service. Ask where you're staying and they will put you in contact with organisers. The day you go sandboarding they will pick you up and take you to the best dunes. Yes, the truck can not climb to the top and you have to walk, which is quite good as it will make you think about the climb up as well as the way down. It can be difficult in the heat to carry boots and a board. But when you're sliding down the dunes with the wind blowing and seeing the sea in the background, it is worth it.