A number of SANF officers served as British liaison officers on ships of the exiled navies, particularly aboard submarines. Most South Africans are bilingual and able to understand Dutch so it makes sense that a few seconded officers and ratings would have found themselves aboard Royal Netherlands Navy ships during WW2. One such was Lt. Brooke Duffy who served on the submarine K-XV, here among her crew at the US Navy Submarine Base New London, March 1943.
I also have my suspicions about Lt. T.D. Vos, (an un-British but very South African surname) aboard O-19 during February 1943.