Groundwater is a key resource throughout southern Africa. Shallow aquifers are generally easy to access, but are often saline and highly vulnerable to contamination. Deep, semi-fossil groundwater resources are difficult to investigate and explore (e.g., spatial extent, volume of stored water, recharge volume, location) but potentially contain large volumes of water of excellent quality. Within SASSCAL, the opportunity to investigate a newly discovered deep aquifer in northern Namibia opened up. This article provides a summary of key findings emerging from research within SASSCAL and previous investigations. In summary, the main findings of these investigations are as follow: i) Fresh-water in the deep Ohangwena 2 (KOH-II) aquifer is not of fossil origin (i.e., recent recharge exists). ii) The recharge area of the KOH-II is located in the foothills of the Angolan highlands. iii) The volume of recharge is low (less than 1 percent of mean annual precipitation). Although these findings need to be confirmed by further scientific studies and additional drillings, especially to determine the exact extent of the aquifer system, the lessons learnt from more than three decades of investigations in this area allow the formulation of a new strategic orientation for groundwater prospecting in southern Africa: Rather than carrying out extensive drilling, the exploration strategy should be carried out similarly to the exploration for hydrocarbons, where first the tectonical boundary conditions and the sedimentological features are determined. This requires transboundary coordination and extensive planning, but it is the only way to systematically investigate deep, supraregional aquifer systems.