Lake Otjikoto is a water filled sinkhole with a known water depth of about 100 metres. It is of historical importance because of the presence of World War I artifacts that were dumped in the lake at the end of the war. Otjikoto is a National heritage site and diving is controlled through a permit system.
Lake Guinas is a water filled sinkhole with a known water depth of about 135 metres. A unique feature of the lake is that the water temperature remains at about 25 degrees all year round irrespective of depth. Guinas is situated on private land and diving is controlled through a concession system.