If you are going up on Table Mountain for the view, go early in the day, because clouds often come in the afternoon.
They used to have an awesome scuba diving option, to get in the water inside a cage, for a shark feeding. Hard to find elsewhere.
Diving with the sharks is an option. It is not scuba it is more stand in a cage and put your head under water to see the sharks. It takes about 4 hours and if you get real sick there is a $500 fee to take you back to land.